Skip to main content

Full text of "Environment of Mesa Verde, Colorado"

See other formats


■ 






L^ 



r 
a 






g^n^ 



PV &UO\ 






OCi 



u 



Ct ^s 






&A»li 



Digitized by the Internet Archive 

in 2012 with funding from 

LYRASIS Members and Sloan Foundation 



http://archive.org/details/environmentofmesOOerdm 



Environment of Mesa Verde, Colorado 



NationalPark Service Archeological Research Series 



1 Archeology of the Bynum Mounds, Mississippi (PB 177 061).* 

2 Archeological Excavations in Mesa Verde National Park, Colorado, 1950 (PB 177 062).* 

3 Archeology of the Funeral Mound, Ocmulgee National Monument, Georgia (PB 177 063).* 

4 Archeological Excavations at Jamestown, Virginia (PB 177 064).* 

5 The Hubbard Site and other Tri-wall Structures in New Mexico and Colorado. 

6 Search for the Cittie of Ralegh, Archeological Excavations at Fort Raleigh National Historic Site, 
North Carolina. 

7-A The Archeological Survey of Wetherill Mesa, Mesa Verde National Park, Colorado. 

8 Excavations in a 17th-century Jumano Pueblo, Gran Ouivira, New Mexico. 

9 Excavations at Tse-ta'a, Canyon de Chelly National Monument, Arizona. 
7-B Environment of Mesa Verde, Colorado (Wetherill Mesa Studies). 

7-C Big Juniper House, Mesa Verde National Park, Colorado (Wetherill Mesa Excavations). 

7-D Mug House, Mesa Verde National Park, Colorado (Wetherill Mesa Excavations). 






"~\ hesc publications are no longer available from the Superintendent of Documents, but may be ordered by title 
(and parenthetical code number) by writing to: Clearinghouse, U.S. Department of Commerce, Springfield, Virginia 22151. 
I hese reports are available in two forms: microfiche at t>>i' per document, or paper copy at $3.00 per volume, prepaid. 



ARCHEOLOGICAL RESEARCH SERIES NUMBER SEVEN-B 



Wetherill Mesa Studies 



environment 



of Mesa Verde, Colorado 



James A. Erdman, Charles L. Douglas and John W. Marr 



CLEMSON UNIVERSITY LIBRARY 
DOCUMENTS DEPT. 



NATIONAL PARK SERVICE /U.S. DEPARTMENT OF THE INTERIOR 
WASHINGTON 1969 




United States Department of the Interior 
Walter j. hickel, Secretary 



This publication is one of a series of research studies devoted to special- 
ized topics which have been explored in connection with the various 
areas in the National Park System. It is printed at the Government 
Printing Office and may be purchased from the Superintendent of 
Documents, Government Printing Office, Washington, D.C. 20402. 
Price $3.50. 




National Park Service 

george b. hartzog, jr., Director 



LIBRARY OF CONGRESS CATALOG CARD NUMBER: 72-600243 



foreword 



From 1959 to 1963, the National Park Service, with generous support from 
the National Geographic Society, made a comprehensive study of the arche- 
ology and ecology of Wetherill Mesa, in Mesa Verde National Park. Wetherill 
Mesa is being developed so that increasing numbers of visitors will be able to 
observe the evolution of a prehistoric Indian culture over some 700 years, 
both here and in the nearby and more familiar section of the park known as 
Chapin Mesa. 

This is the second monograph of the Wetherill Mesa Project. The report 
not only provides substantive data on environmental variations at Mesa 
Verde and their bearing on the prehistoric settlement pattern and land use 
of the area, but also demonstrates the critical importance of such research to 
a fuller understanding of human ecology of the past elsewhere. James A. 
Erdman, now with the U.S. Geological Survey, Denver, and Charles L. Douglas, 
now on the staff of the Texas Memorial Museum, University of Texas, 
Austin, came to the Wetherill Mesa Project from the Institute of Arctic and 
Alpine Research, University of Colorado, in Boulder. John W. Marr is 
director of the Institute. 

Additional reports in the Wetherill Mesa series will deal with several other 
aspects of the archeology and ecology of the area. 




George B. Hartzog, Jr. Director 




-**<,*♦ I* 






. if? 




**T w^ 










US 












'V«fivi 



■***$ 



ia>, 



;. . v •. 






l?$?w 



acknowledgments 



Without the contributions of many agencies and individuals this aspect of 
the scientific program of the Wetherill Mesa Project could not have been 
carried out. 

First and foremost, our thanks go to the National Geographic Society, 
which provided financial support for the work. 

We are grateful to the Ute Mountain Utes for granting permission to 
operate the station at the Lowest Mesa-top Site, M-l, on tribal lands. 

The Institute of Arctic and Alpine Research, Boulder, Colo., organized 
and furnished some of the equipment for the research. Markley W. Paddock 
devised the initial program design and planned the instrumentation; John 
Clark supervised the installations; and David M. Gates, formerly of the 
National Bureau of Standards, Boulder Laboratories, and consultant to the 
Institute, assisted with the interpretation of the solar radiation data. 

Appreciation is extended to William C. Bradley of the Geology Depart- 
ment, University of Colorado, for his advice on the section on geology and 
soils, and to William A. Weber of the University of Colorado herbarium for 
providing current plant nomenclature and for verifying critical material. 

We are grateful to Harold C. Fritts and David G. Smith of the Laboratory 
of Tree-Ring Research, University of Arizona, for help with the data analysis. 
Fritts was responsible for enabling us to reduce and analyze the data through 
the University of Arizona's Computer Center, and made valuable suggestions 
in our interpretations. Smith was involved in the data handling both at 
Mesa Verde National Park and at Tucson. Our thanks go to him and to 
Thomas P. Harlan, also of the Tree-Ring Laboratory, for the dates for modern 
cores and burned samples collected at Park Point in Mesa Verde. 

We are indebted to the Numerical Analysis Laboratory of the University 
of Arizona for donating computer time and for analyzing the environment 
data. Robert L. Baker of the Laboratory's Systems Engineering Department 
programed the monthly summaries. 

For a better understanding of the Mesa Verde soils, and specifically for 
the profile descriptions of each station site, we are grateful to Orville A. 
Parsons of the Soil Conservation Service, Fort Collins, Colo. Parsons' reading 
of the manuscript is also appreciated. 



Our thanks go to George A. King, architect, of Durango, Colo., who 
drafted the base map of Mesa Verde. 

Our thanks go to the following members of the Wetherill Mesa Project 
staff: to laboratory assistants Pauline Goff, Natalia Ellis, and Ruth Chappell 
for data handling and preliminary analysis; to Marilyn Colyer for her help 
in the field on vegetation analysis and for the preparation of the graphs ; and 
to project photographer Fred E. Mang, Jr., whose pictures were often taken 
under less-than-ideal conditions and from some rather hazardous spots. 
His sense of the fitting, yet dramatic, photograph gives our report a dimension 
it would not otherwise have had. 
This publication is Contribution 41 of the Wetherill Mesa Project. 

J. A. E., C. L. D., and J. W. M. 



10 



contents 



Chapter 1 INTRODUCTION, page 15. 
Geology and Soils, page 15. 
Vegetation,/;^ 17. 
Climate, page 18. 

Chapter 2 DESIGN OF THE STUDY, page 21. 

Environment Factor Measurements, page 21. 

Chapter 3 DESCRIPTION OF THE STANDS, page 27. 
Lowest Mesa- top Site, M~\,page 27. 
Middle Mesa-top Site, M-2, page 31. 
Highest Mesa-top Site, M-3, page 34. 
Canyon-bottom Site, C-2, page 38. 
Southwest Exposure Canyon -slope Site, C-l, page 41. 
Northeast Exposure Canyon -slope Site, C-3, page 44. 

Chapter 4 DISCUSSION OF SITE INTERRELATIONS, page 47. 
Soil and Vegetation Relationships of Selected Sites, page 47. 
Comparison of 1962 and 1963 Weather, page 47. 
Comparison of Individual Factors between Sites, page 48. 
Comparison of Weather Bureau Station and M-2 Site, page 52. 
Comparison of Mesa- top Sites, page 52. 

Comparison of Middle Mesa-top and Canyon- bottom Sites, page 54. 
Comparison of Canyon Sites, page 55. 

Chapter 5 THE ENVIRONMENT AND THE PREHISTORIC OCCUPATION,/;^ 57. 

Evidence of Prehistoric Climate, page 57. 

Influence of Environment on the Puebloan Culture, page 57. 

REFERENCES , page 59. 

APPENDIX : Annual Summaries of Environment Data, page 61. 



11 



illustrations 



1 Map of Mesa Verde National Park and vicinity, showing location of environ- 
ment measurement sites, page 16. 

2 Recording instruments at M-2, page 22. 

3 A 3-cup totalizing anemometer atop tree at canyon-bottom site, page 23. 

4 Characteristic vegetation at M-l 3 page 24. 

5 M-2 site near park headquarters, page 25. 

6 Characteristic vegetation at M-2, page 31. 

7 M-3 site at North Rim, in late winter, page 32. 

8 Black sagebrush-grass community near M-3, page 34. 

9 Oak thicket, recovered from mid- 19th century burn, near M-3, page 35. 
10 Navajo Canyon setting of canyon-bottom and slope sites, page 37. 

1 1 C-2 site at bottom of Navajo Canyon, page 39. 

12 CI site on west-southwest-facing slope in Navajo Canyon, page 41. 

13 C-l instrument shelter and surrounding area, page 42. 

14 C 3 instrument shelter and surrounding area, across the canyon from C-l, page 
43. 

15 Graph showing soil moisture content and precipitation at the six sites in 1962 
and 1963, page 49. 

16 Graphic comparison of monthly precipitation in 1962 and 1963 at the mesa-top 
sites and at the canyon-bottom site, page 50. 

1 7 Graph showing relationship of air temperatures to exposure under cloudless 
skies in June and December 1963 at the canyon-slope sites, C-l and C-3, page 51. 

IP) Air-temperature profiles of the west-south-west-facing slope in Navajo Canyon, 
showing pronounced cold-air drainage at the bottom and the "thermal zone" 
on the talus, page 52. 

19 Graph showing average wind velocities at the mesa-top and at the canyon- 
bottom sites in 1962 and 1963, page 53. 

20 Graph showing progressions of five climatic variables at M-2 and C-2 sites on a 
cloudless day, pages 54-55. 

21 Map showing locations of prehistoric farming terraces on Wetherill Mesa and in 
adjacent canyons, page 58. 



12 



tables 



1 Weather data, Mesa Verde National Park, page 19. 

2 List of species observed in the environment measurement sites, pages 28-29. 

3 Tree data at M-l, page 30. 

4 Soil profile underlying M-l juniper-pinyon/bitterbrush stand, page 30. 

5 Soil moisture constants in percent dry weight, page 30. 

6 Some climatic factors of the mesa-top sites, page 33. 

7 Tree data at M-2, page 33. 

8 Soil profile underlying M-2 pinyon-juniper/mutton grass stand, page 36. 

9 Soil profile underlying M-3 mountain brush vegetation, page 36. 

10 Soil profile underlying C-2 big sagebrush/cheatgrass stand, page 38. 

1 1 Some climatic factors of the canyon sites, page 40. 

12 Tree data at C-l, page 44. 

13 Soil profile underlying the C-l juniper-pinyon/big sagebrush stand, page 44. 

14 Tree data at C-3, page 45. 

15 Soil profile underlying C-3 pinyon-juniper/mountain brush stand, page 45. 



13 



-•••Wi** 






— -**V 



J£- 



VVf 



4«L r >., 



l £yF**r \ 



?}&* 



r4; 



»■ 






* • ■ * 



m 



'■' ' 



^whu 



■- '■ 'bK 



IK 



'•..-;■'.,-. 



'' -V 



3 



H0fw 



9H 



-^ -T- , .»» \' V* 



^^«338gfc 






CHAPTER 1 



introduction 



Mesa Verde is an imposing landmass that rises abruptly above the semiarid country of southwestern 
Colorado. It is a relatively flat tableland, between the high San Juan massif to the northeast and 
and the lower desert to the southwest. The mesa lies on the eastern edge of the Colorado Plateau 
physiographic province, "a land of gently folded sedimentary rocks eroded on a majestic scale into 
broad plateaus, precipitous mesas and buttes and dark canyons" (Hack, 1942, p. 3). This great 
landmass dips gently over a 15-mile stretch from an elevation of 8,500 feet at the northern escarp- 
ment to about 6,500 feet at the southern end. The mesa is not an unbroken tableland, as its Spanish 
name suggests. It is more a plateau than a mesa, but usage has firmly established the latter term. 
Moreover, scores of canyons dissect the once continuous surface into somewhat isolated segments, 
each of which is locally called a mesa (fig. 1). 



Mesa Verde is fascinating not only because of its spec- 
tacular terrain and interesting geology and biology, but 
because of its prehistoric occupation by aboriginal man. 
For about 700 years, up to the close of the 13th century, 
Pueblo Indians lived and farmed successfully here under 
difficult climatic and soil conditions. Their impact on 
the landscape is still visible in numerous and varied 
dwelling sites, midden deposits (often supporting sage- 
brush where forest normally occurs), and agricultural 
check-dam systems. What other features are ascribable 
to the Indians' activities constitute a tantalizing problem 
for ecologists. Following its abandonment around A.D. 
1300, the mesa was essentially undisturbed until white 
settlers began moving into the area in the 1870's. 

Part of the mesa became Mesa Verde National Park 
in 1906, but the landscape is so rugged that few studies 
had been made of the soils, atmospheric factors, biota, 
and ecological processes within it. The Wetherill Mesa 
Project provided an opportunity to fill many gaps in our 
knowledge of the total Mesa Verde environment. This 



report is concerned primarily with quantitative data on 
the atmospheric factors and vegetation of representative 
stand ecosystems in Mesa Verde. 

GEOLOGY AND SOILS 

The Mesa Verde is composed of marine sediments of 
Upper Cretaceous age. These rocks form a discrete geo- 
logical unit, the Mesaverde group, whose members 
include the Cliff House sandstone, the Menefee forma- 
tion, and the Point Lookout sandstone. The resistant Cliff 
House sandstone caps the mesa and is underlain by the 
Menefee formation, a coal-bearing deposit that outcrops 
on the steep canyon slopes. The lowest and least con- 
spicuous member is the Point Lookout sandstone, ex- 
posed along the North Rim and in the deeper canyons 
of the south and west extremities of the mesa. The top 
two layers are primarily responsible for the rugged 
canyon-mesa terrain so characteristic of the area. 

Headward erosion of the canyons, perhaps during more 



15 




Mesa Verde National Park and vicinity, showing locations 
of environment measurement sites. 



16 



moist climatic regimes, produced numerous large alcoves 
situated along the upper cliffs, many of which contain 
the ruins of cliff dwellings built by the prehistoric 
Indians. These alcoves have been sculptured by spring- 
sapping, a weathering process that weakens and under- 
cuts the sandstone cliffs where they are in contact with 
the impervious shale strata. To a lesser degree, some of 
the shallower alcoves, called exfoliation caves, have 
resulted from release of confining pressures when erosion 
exposed rocks that were once deeply buried. (For 
further information on cave origins of this type, see 
Bradley, 1963.) 

The regional and local geology have been described by 
Douglas Osborne (in Hayes, 1964). Osborne's discussion 
is based largely on the work of Hunt (1956) and Wanek 
(1959). 

The soils are primarily wind-deposited loess in origin 
(Arrhenius and Bonatti, 1965), although along the upper 
reaches of Mesa Verde some residual soils are developed 
from weathered sandstone. Soil depth is extremely 
variable. Deep profiles occur at the heads of canyons, 
on alluvial-colluvial terraces, on the canyon floors, and 
on the broad mesa where the loess soil may reach depths 
of 15 feet. But soils are either very shallow or nonexistent 
in the mesa-top drainages and rim areas, on the canyon 
talus slopes, and on the narrow, more easily eroded ridges 
of the northern third of the mesa. 

The carbonate content of the underlying sandstone, 
and consequendy of the soils, also varies considerably. 
In the brush zone along the North Rim, the residual 
soils are darker colored and slightly acid, with little or 
no free lime (Roberts, MS.). They contrast sharply with 
the almost white, flaky soils encountered in the juniper- 
dominated woodland toward the southern end of the 
mesa. In this area the soil surface is highly calcareous, 
which may be due to different parent material, less 
precipitation, and higher temperatures. 

Trewartha (1954, p. 286) states that "steppe [or semi- 
arid] lands are often the recipients of large amounts of 
fine dust or loess blown out of the drier and less well 
protected deserts." Because of the relatively meager 
rainfall, leaching is not a serious detriment to soil pro- 
ductivity. Mineral plant foods are usually abundant. 
"Yet, because of the low and variable rainfall in which 
they develop, and to which they largely owe their qual- 
ity, [semiarid lands] are not extensively used for crop 
production. It is the old story of fruitful soils and prolific 
climates seldom being areally coincident" (ibid). 
Nonetheless, as will be shown later, the prehistoric 
Pueblo Indian farmers made use of the Mesa Verde 
soils to a remarkable extent. 

More detailed edaphic information is available in the 
soil reconnaissance reports of Wetherill Mesa by Roberts 
(MS.) and White (MS.). A standard soil survey of the 
area, made by Orville A. Parsons, will be published as a 
report of the Wetherill Mesa Project. 



VEGETATION 

The plants of Mesa Verde are part of the Sierra 
Madrean flora that occupies the Great Basin, Colorado 
Plateau, and the Sierra Madre of northern Mexico 
(Benson, 1957, p. 598). Vegetal material identified from 
the Wetherill Mesa Project's excavations and earlier 
collections indicate a prehistoric flora similar to that of 
the present day (Welsh, MS.). 

Ecologically, the mesa is in the pinyon-juniper climax 
region that forms the lowest forest zone in the Rocky 
Mountains and is the only zone present on many of the 
low ranges of the Great Basin. The total geographic 
range of the climax region extends from eastern Oregon 
and southern Idaho southward along western Colo- 
rado, northeastern Arizona, and New Mexico. The trees 
at Mesa Verde grow relatively tall (up to 35 feet) and 
close together, producing a pinyon-juniper type unlike 
the scrubby trees in an open "pygmy woodland," which 
are characteristic of the climax region generally. 

The almost continuous mantle of pinyon-juniper trees 
over the mesa gives an impression of monotonous homo- 
geneity when viewed from the air. Walking through the 
forest, however, you find a surprising variety of plants. 
These plants are organized into several different stand- 
types because of subde variations in slope, altitude, soil, 
the effects of fires, and the influences of prehistoric man. 

Pinyon pine (Pinus edulis) and Utah juniper (Juniperus 
osteosperma) are the dominant trees, but there are some 
small stands of Douglas-fir {Pseudotsuga menziesii), aspen 
(Populus tremuloides), and ponderosa pine (Pinus ponderosa) . 
Cottonwood (Populus fremontii) and Rocky Mountain 
juniper (Juniperus scopulorum) are scattered throughout 
the area, the latter common along the northern escarp- 
ment. Douglas-fir, the most abundant of these less com- 
mon trees, occurs in sheltered side canyons, seep areas, 
and at the higher elevations. It is the source of the names 
"Spruce Canyon" and "Spruce Tree House," probably 
through an error in identification. Aspen is restricted to 
the coves of the North Rim and some of the more moist 
and protected canyon sites. There are only a few scat- 
tered stands of ponderosa pine, and reproduction is 
limited. Gambel oak (Quercus gambelii) and Utah service- 
berry (Amelanchier utahensis) are the dominants in a shrub 
zone caused by recurrent fires along the higher parts 
of the mesa, while big sagebrush (Artemisia tridentata) is 
common on the sandy loam terraces along the canyon 
floors and also on some prehistoric trash deposits on top of 
the mesas. 

Fire has had an important effect on the vegetation. A 
reconnaissance of the larger burns and a study of aerial 
photographs show that fires have been more common 
in the higher, north part of the mesa than in the lower 
areas. Possibly the prehistoric Indians deliberately 
burned these upper parts of the mesa, which are of mar- 
ginal farming value, in order to maintain the shrub 



17 



271-475 0-69— 2 



vegetation, which supports a heavier game population 
than a pinyon-juniper forest approaching climax. Many 
fires, however, were undoubtedly started by lightning. 
The mountain brush vegetation in the North Rim area 
is relatively unstable. Pinyon reproduction has increased 
as a result of stringent fire-protection measures by the 
park, and the area is gradually becoming reforested. 

The present-day vegetation probably closely resembles 
that which flourished before the prehistoric Indians en- 
tered the area. To be sure, today's dense oak thickets on 
abandoned terraces and on reservoirs behind check 
dams, as well as concentrations of sagebrush on many 
midden sites, were lacking in preoccupation time. But 
these vegetation units occupy only a small part of the 
mesa. As long as the Indians were active in the area, the 
vegetation was probably a patchwork of forest, agricul- 
tural fields, and brushland. Sagebrush may have been 
more abundant than it is today. It would have grown 
rapidly in abandoned fields and burned areas, and it 
was used in quantity for roofing material in the pre- 
historic structures. After the Indians left, the vegetation 
pattern changed through natural ecological processes 
and in due course most of the region returned to preoccu- 
pation conditions. 

CLIMATE 

According to Koppen's classification of world climates 
based on annual and monthly means of temperature 
and precipitation, Mesa Verde has a cold, middle lati- 
tude, semiarid climate (BSk of the Koppen system, see 
Trewartha, 1954, pp. 225-226). Trewartha (op. cit., 
p. 268) observes: "In general, the steppe [or semiarid 
type of dry climate] is a transitional belt surrounding 
the real desert and separating it from the humid climate 
beyond." Though it lies in an area of dry climate, Mesa 
Verde is closer to a humid than to a desert climate be- 
cause of the proximity of the San Juan Mountain massif 
to the northeast and of the rest of the southern Rocky 
Mountains farther east. 

The following statements by Trewartha (op. cit.) are 
pertinent to the intermountain region of which Mesa 
Verde is a part: 

Dry climates in the middle latitudes usually are 
found in the deep interiors of the great continents, 
far from the oceans, which are the principal sources 
of the atmosphere's water vapor. Further intensifying 
the aridity of the deep continental interiors is the 
fact that in both Eurasia and North America these 
locations are commonly surrounded by highlands 
that block the entrance of humid maritime air 
masses and of rainproducing storms (p. 280). 

The essential feature of a dry climate is that 
potential evaporation from the soil surface and from 
vegetation shall exceed the average annual precipi- 
tation. In other words, during a normal year the 
capacity of the atmosphere to acquire water evaporated 



from the soil surface and transpired from plants is 
greater than the water added to the soil through 
precipitation. In such a climate there is a pre- 
vailing water deficiency and a constant ground- 
water supply is not maintained, so that permanent 
streams cannot originate within such areas. It may 
be possible, however, for permanent streams to 
cross areas with dry climates . . . provided they 
have their sources in more humid regions (p. 267). 

The Mancos River, which borders Mesa Verde and 
drains its many canyons, has its headwaters in the 
La Plata Mountains to the north. Within the mesa 
proper the only natural water supply available to 
man and other animal life comes from springs and 
seeps in the canyons. 

A climatic summary of the immediate region is ex- 
cerpted from Gittings (1941, p. 808): 

The distinct climatic feature of the western section 
[of Colorado] ... is the comparative uniformity of 
the weather from day to day. Severe cold waves, 
common on the eastern plains, are comparatively 
rare. . . . There is a tendency for a high-pressure 
area to form in western Colorado in winter and to 
remain stationary for several days. When such a pres- 
sure distribution controls the weather, the sky is clear, 
the day temperatures are moderately high and uni- 
form, and the nights are cold, though seldom exces- 
sively so except when the ground is covered with snow 
and where the air drainage is poor. Night tempera- 
tures depend largely on the topography, air drainage 
exerting a greater control than does the actual eleva- 
tion. ... In western sections of the State the most 
important part of the precipitation occurs in winter 
and early spring; January, February, and March are 
the months of heaviest snowfall. . . . In southwestern 
counties there is a marked tendency toward drought 
in late spring and early summer ; June is practically 
rainless. 

The following account of the recent climate of Mesa 
Verde is taken from the 41 -year record (in part, shown 
in table 1) of the U.S. Weather Bureau station near the 
Mesa Verde National Park headquarters, and from a 
discussion by Erdman (MS.). The approximate location 
of the station is lat. 37° 12' N. and long. 108° 29' W. Its 
position and elevation (7,070 feet) make it as representa- 
tive of the Mesa Verde physiographic unit as possible. 
Since 1923, the average annual precipitation has been 
18 inches. The late winter months constitute one of the 
"wet seasons," February being one of the wettest months 
of the year with almost 2 inches of moisture. Most of the 
moisture during this period occurs as snow. Winters seem 
to be relatively mild, perhaps because of the predomi- 
nantly sunny days. January, the coldest month, has a 
mean temperature of 29° F. and 19 inches of snowfall. 
The coldest recorded temperature ( — 20° F.) occurred 
during the severe nationwide cold wave of January 1963. 
According to Trewartha (1954, p. 181), in this climate 
"the winter season has many more large and steep- 
gradient cyclones and anticyclones than summer, so that 



18 



TABLE 1.— WEATHER DATA, MESA VERDE NATIONAL PARK 

United States Weather Bureau station, Chapin Mesa, elevation 7,070 feet. Deviation of the 1962 and 1963 annual summaries from the 41-year record (1923-63) 







Air temperature 


, in degrees Fahrenheit 










Precipitation, 


in inches 




















Mean of 
















Maximum 


Minimum 


Mean 


maximum 


Mean 


minimum 


maximum 




Water 






Snow 




Month 
















and 


minimum 
















41- 


Deviation 


41- 


Deviation 


41- 


Deviation 


41- 


Deviation 


41- 


Deviation 


41- 


Deviation 


41- 


Deviation 




year 
record 




year 
record 




year 
record 




year 
record 






year 
record 




year 
record 






year 
record 








































1962 


1963 




1962 


1963 




1962 


1963 




1962 


1963 




1962 


1963 




1962 


1963 




1962 


1963 


Jan. 


62 


-9 


-15 


-20 


4-14 





40 


-1 


-7 


18 


-2 


-7 


29 


-1 


-7 


1.68 


-.97 


+ .01 


19.4 


-7.7 


-.2 


Feb. 


68 


-9 


-3 


-15 


4-13 


+ 18 


45 


-1 


+ 3 


22 


+ 2 


+ 3 


33 


+ 1 


+ 3 


1.82 


+ .51 


- .44 


17.6 


+ 5.8 


-8.6 


Mar. 


72 


-5 


-3 


4 





+9 


50 


-4 


+ 2 


26 


-3 





38 


-4 


+ 1 


1.74 


-.41 


-.91 


13.6 


+3.8 


-5.6 


Apr. 


84 


-4 


-9 


9 


+ 15 


+ 2 


61 


+ 5 





34 


+4 


-2 


48 


+4 


-1 


1.37 


-.92 


-.69 


4.5 


-4.5 


— 1.5 


May 


90 


-10 


-8 


23 


+ 5 


+ 18 


71 





+6 


43 


-2 


+4 


57 


-1 


+ 5 


.98 


+ .09 


-.87 


.4 


- .4 


- .4 


June 


101 


-11 


-7 


32 


+ 9 


+ 7 


83 


-1 


+ 1 


52 


-1 


-1 


68 


-2 


-1 


.67 


- .51 


-.60 


t. 








July 


102 


-9 


-6 


43 


+ 8 


+ 10 


88 


-1 


+ 1 


57 


+ 1 


+ 2 


72 





+ 2 


1.76 


-1.39 


+ .30 











Aug. 


101 


-5 


-11 


41 


+8 


+ 10 


85 


+ 3 


-2 


56 


+ 2 





70 


+ 3 





2.16 


-1.95 


+2.20 











Sept. 


94 


-4 


-8 


28 


+ 9 


+ 18 


78 





+ 2 


49 


+ 2 


+4 


63 


+2 


+4 


1.69 


+ .38 


-.49 


.2 


- .2 


- .2 


Oct. 


85 


-9 





13 


+ 22 


+ 20 


66 


+ 1 


+ 5 


39 


+2 


+ 7 


52 


+ 2 


+ 6 


1.63 


+ 1.02 


+ .15 


.9 


- .9 


-.9 


Nov. 


75 


-8 


-3 


-3 


+ 18 


+ 20 


51 


+ 3 


+ 3 


28 


+ 5 


+ 2 


40 


+4 


+ 2 


1.03 


+ .66 


-.32 


5.5 


+ .4 


-2.5 


Dec. 


67 


-10 





-6 


+8 


+8 


42 


+ 3 


+ 1 


21 


+2 


-1 


32 


+ 2 





1.62 


-.31 


-1.00 


16.0 


-9.7 


-8.0 


Year 


102 


-6 


-6 


-20 


+ 14 





63 


+ 1 


+ 2 


37 


+ 1 


+ 1 


50 


+ 1 


+ 1 


18.15 


-3.80 


-2.66 


78.1 


-13.4 


-27.9 



the cooler seasons have more variable weather than the 
warmer periods of the year." This proved to be the case 
in our own observations: temperatures were more varia- 
ble during the winter than during the summer months. 

Winter moisture is a critical factor as it determines the 
vegetational aspect of the landscape in late spring and 
early summer, typically the driest period of the growing 
season. Annuals and some perennials are highly depend- 
ent upon the surface moisture during these periods of 
low rainfall. 

Although July is the hottest month of the year, with a 
mean temperature of 72° F. and a maximum of 102° F., 
the heat is tempered by rains which normally begin about 
this time of year. Rainfall reaches its peak in August 
(average of 2 inches) and decreases gradually into the 
autumn. During the late summer months the days begin 
with cloudless skies, but by noon, because of intense air 
turbulence, cumulus clouds develop and thunderstorms 
are common. Precipitation is usually localized and in- 
tense for a short period of time. Consequendy, runoff is 
high and the precipitation is not nearly so effective as 
winter and spring precipitation in controlling the 
growth of indigenous plants. 

During 1962 and 1963, Mesa Verde experienced sub- 
normal rainfall and above-average temperatures, the 
latter occurring especially throughout the autumn 
months (table l.i). Although the amount of precipitation 
between the 2 years did not differ appreciably, its 
pattern varied gready. A sustained dry period prevailed 
throughout most of 1962, broken finally by heavy rains 
in the fall. The precipitation record approached the 
normal pattern the following year, although May and 



June were unusually dry and August was abnormally wet. 

Lightning-induced fire is a perennial threat to parched 
vegetation. Prehistoric burns in the northern third of 
Mesa Verde National Park and on several large tracts 
in the southern part of the park were undoubtedly 
caused by lightning. More recendy, in July 1934, a 
lightning fire burned about 5,000 acres on the northern 
third of Wetherill Mesa and adjacent areas (Watson, 
1934, pp. 16-17). And in July 1959, lightning ignited a 
fire that burned 3,043 acres of forest and brush in Mor- 
field Canyon in the southeastern part of Mesa Verde. 
Fire as a byproduct of summer storms has been an im- 
portant ecological factor in the area. 

In considering the relationship of man to his environ- 
ment, a subject of no small importance in the pre- 
historic and present-day occupation of the region, 
Trewartha (1954, p. 283) makes this comment: 

Because of the greater precipitation than in 
deserts, the steppes are somewhat better fitted for 
human settlement, but this, together with the un- 
reliable nature of the rainfall, also makes them 
regions of greater economic catastrophe. A succession 
of humid years may tempt settlers to push the agri- 
cultural frontier toward the desert, but here also 
drought years are sure to follow, with consequent 
crop failure and ensuing disaster. 

In essence, then, and as we might well expect, the 
semiarid, broken Iandmass we call Mesa Verde suffers 
from erratic rainfall that affects not only plant and 
animal life but man, especially when his main suste- 
nance derives from the soil itself. 



19 



design of the study 



The scientific program of the Wetherill Mesa Project as 
envisioned by the project's supervisor, Douglas Osborne, 
included not only comprehensive archeological investi- 
gations on Wetherill Mesa but studies of the total environ- 
ment of the Mesa Verde area. One approach in the latter 
range of studies was to obtain and compare precise 
quantitative data on selected environmental factors at 
sites that differed from one another in elevation or to- 
pography, over a period of at least 2 years. Such data on 
the present environment, it was reasoned, would contrib- 
ute to studies of possible changes in the environment of 
the past, and ultimately lead to a fuller understanding 
of the prehistoric occupation of the area. 

Since the Institute of Arctic and Alpine Research had 
operated an environment measurement program on the 
eastern slope of the Front Range in Colorado for 9 years 
(Marr, 1961), Osborne invited Marr and the Institute 
staff to plan the study, select and install the instruments, 
and provide technical supervision of the operation. Two 
of the authors, Erdman and Douglas, ecologists on the 
Wetherill Mesa Project staff, serviced the instruments 
and processed the data. As the study progressed, they 
made numerous improvements in the initial design and 
procedures. Other Wetherill Project personnel contrib- 
uted in a variety of ways. 

Harold C. Fritts of the Laboratory of Tree-Ring Re- 
search, University of Arizona, worked out, with Osborne, 
a dendroclimatological study to be integrated with the 
environment program. Its objective was to provide a 
basis for using tree rings as indicators of past climates 
(Fritts, Smith, and Stokes, 1965). 

Six sites were chosen as samples of the environment 
gradient induced by changes in elevation along the tops 
of the mesas and by differences in topography within 
the canyons. The mesa-top sites were on Chapin Mesa 
and Park Point, and the canyon sites were in Navajo 



Canyon to the west (fig. 1). These sites, rather than sites 
on and adjacent to Wetherill Mesa, were chosen be- 
cause of their accessibility to year-round visitation. 



Station 


Elevation, 
feet 


Location 


M-l 


6,650 


Near the south end of Chapin Mesa. 


M-2 


7, 150 


About 5 miles north of M-l and near park 


M-3 


8,575 


headquarters. 
About 5 miles north of M-2 on Park Point, 
the highest point of Mesa Verde. 


C-l 
C-2 


6,500 
6,382 


West-southwest exposure slope. 
Canyon floor directly below and between 
C-l and C-3. 


C-3 


6,500 


Directly opposite C-l on northeast exposure 
slope. 



We studied stand ecosystems (Marr, 1961) and col- 
lected information on the vegetation and soil as well as 
the weather. Since organisms, environment factors, and 
processes are interrelated, by knowing one an estimate 
can be made of the other components. For example, an 
area with vegetation and soil similar to our C-l station 
probably has a similar total environment. 

ENVIRONMENT FACTOR 
MEASUREMENTS 

Measurements were taken from September 1961 
through December 1963. The main body of data deals 
with solar radiation, air and soil temperature, precipita- 
tion, relative humidity, evaporation, wind, and soil 
moisture. In addition, at each station during the weekly 
servicing visit, observations were made on the type and 
amount of cloud cover, wind direction and velocity, 
and the depth and extent of snow cover. Stations were 
located in clearings where the effect of vegetation on the 
factors measured would be minimal. The hygrothermo- 



21 




2 Recording instruments at M-2. Within the shelter are a hygro- 
thermograph, a 3-pen mercury thermograph, and maximum- 
minimum thermometers. On the roof is a pyrheliometer, and 
mounted on the side is an atmograph. 

graphs and recording units of soil thermographs were in 
a standard Weather Bureau cotton region-type instru- 
ment shelters, with the floor about 4 feet above ground 
in each instance (fig. 2). The shelters were erected in 
the summer of 1961 and dismantled in the spring of 1964 
after our study was completed. 

The environment factors, except soil moisture, and the 
instrumentation for them are listed below: 



The pyrheliometer was mounted on the top, and the 
atmograph was attached to one side, of each shelter. 
Rain gages were mounted on individual supports with 
their rims about 4 feet above the ground. Anemometers 
were mounted on a tree (fig. 3) or on utility poles (figs. 4 
and 5), so that the instruments were several feet above the 
general level of tree crowns. Soil samples for gravimetric 
measurement of water content were collected at the 
edges of the clearings. 

The Piche atmograph records evaporation from a 
standard 5.0 cm. filter disk provided with a continuous 
supply of distilled water; during dry intervals of high 
evaporation, we substituted 3.0 cm. filters. Wet and dry 
bulb temperatures were determined with a Bendix 
motor-aspirated psychrometer at each station visit when 
humidity was reasonably stable. These data verified the 
accuracy of the hygrograph record. Weather Bureau- 
type maximum and minimum thermometers mounted 
on the inside wall of the instrument shelter were read 
and reset at each servicing; these data gave a check on 
the accuracy of the thermograph trace. As a check of 
accuracy for the soil thermographs, a Kahl asphalt-type 
skewer thermometer was periodically inserted to the 
depth of each soil-temperature sensing unit. 

Some difficulties were encountered over which we had 
no control. In spite of careful tests in the laboratory 
prior to installation, the M-2 and C-3 soil thermographs 
went out of adjustment for short periods, the M-2 
instrument during the fall of 1962 and the C-3 instru- 
ment during November and December 1962. Also, 
recent calibration tests of the pyrheliometers suggest 
that although the instruments were in excellent agree- 
ment with one another the values recorded may have 
been higher than those which actually occurred. 

The stations were serviced each week and on the last 
day of each month, all stations being visited on the same 
day except when adverse weather precluded this. 
Erdman or Douglas evaluated the raw data of each 
servicing in search of possible errors. Any adjustments 
indicated were recorded on the original data sheet or 
chart. Laboratory assistants transferred the data to 
initial summary tables. In the case of solar radiation, 



Factor 



Instrument 



Station 



Recording 



Solar radiation 

Air temperature 

Soil temperature at 2, 6, and 

12 inches. 
Precipitation 

Relative humidity 

Evaporation 

Wind 



Belfort pyrheliometer 

Belfort hygrothermograph 

Bendix-Friez hygrothermograph 

Kahl 3-pen remote sensing mercury 

thermograph. 
Standard 8-inch diameter precipitation 

gage. 
Belfort hygrothermograph 

Bendix-Friez hygrothermograph 

Piche atmograph 

Bendix-Friez or Belfort 3-cup totalizing 
anemometers. 



M-2 and C-2 

M-2, M-3, C-l, C-2, and 
C-3. 

M-l 

All stations 

M-l, M-2, M-3, and C-2 

M-2, M-3, C-l, C-2. and 
C-3. 

M-l 

M-l, M-2, M-3, and C-2 

M-l, M-2, M-3, and C-2 



Continuous. 
Do. 

Do. 
Do. 

Weekly and monthly totals. 

Continuous. 

Do. 
Continuous from May 

through October. 
Weekly and monthly totals. 



22 



this task involved measurement of the area under the 
daily traces on the pyrheliograph chart with a compen- 
sating polar planimeter. This area under the curve was 
then converted to a gram calorie unit (gm. cal./cm. 2 / 
day) by computer at the Numerical Analysis Center at 
the University of Arizona. 

Correctness of the data transfer was insured by two 
laboratory assistants working together, one reading the 
original data and the other checking figures on the data 
transfer sheet. The initial data summaries were trans- 
ferred to IBM punch cards at the Numerical Analysis 
Center. An IBM 1401 program, produced by Robert 
Baker, computed the daily means, monthly totals, and 
monthly averages, and printed the monthly summary 
tables. At Mesa Verde, annual summaries (see ap- 
pendix) were compiled from the monthly summaries. 

The summaries were checked by Marr and Institute 
assistants by comparing the data from the different 
stations and tracing apparently odd relationships back 
to the original data. (The original charts and printed 
and punched monthly summaries are filed at the 
Institute of Arctic and Alpine Research and are available 
for study by interested scientists.) 

Soil Studies 

The descriptions of soil profiles used in this report 
were supplied by Orville A. Parsons. The soil moisture 
constants of percent moisture at )i and at 15 atmospheres 
(field capacity and permanent wilting percentage 
equivalents, respectively) were determined by pressure 
membrane techniques for soils collected at each station. 
The samples were collected and screened through a 
2 mm. sieve at Mesa Verde. Measurements were made 
by the Department of Agronomy, Colorado State 
University, Fort Collins. 

In order to determine how much the moisture tension 
values were in accord with the actual permanent wilting 
points of these soils, wheat seedlings were planted in 
four replicate samples of the soils from stand M-2, and 
the soils were allowed to dry until permanent wilting 
was reached. The percentage of moisture was then 
determined for each sample. The following results show 
the close agreement between the pressure membrane 
method and the seedling wilt method : 



Sample 


depth 


15 atmospheres 


Permanent wilting 
point 




Percent 
moisture 


Range 


Percent 
moisture 


Range 


2 inches 


7. 1 

10.6 

9.3 


2.2 
5.2 
2.2 


7.5 

10.6 

9.8 


2 2 


6 inches 

12 inches 


1.2 
2. 5 








3 A 3-cup totalizing anemometer atop tree at the canyon- 
bottom site. 






23 




24 




5 M-2, near park headquarters on Chapin Mesa, at 7,150 feet elevation, looking southwest. Note pioneer vegetation on the abandoned 
dirt tennis court. 



Vegetation Studies 

Native vegetation is regarded as the best expression of 
the totality of a climate. Koppen selected many of his 
climate boundaries with vegetation limits in mind (Tre- 
wartha, 1954, p. 225). The understory and, indeed, the 
appearance of the trees themselves serve as valuable 
indicators of the local environment. 

Erdman studied the vegetation of each stand, using 
the point quarter method of Cottam and Curtis (1956) 
for features of mature trees, and ten 4- by 50-foot belt 
transects spaced at 25-foot intervals for tree reproduction 
data. Categories used in the reproduction study were: 



seedlings = less than 1 foot high; saplings = stems less 
than 2 inches in diameter; trees = stems more than 2 
inches in diameter. A list was made of species observed 
in each community (see ch. 3, table 2), using the nomen- 
clature in the checklist by Welsh and Erdman (1964), 
with certain up-to-date changes furnished by William A. 
Weber. Increment cores were collected from representa- 
tive pinyons to get an estimate of the age of the stands. 
Dating of these samples was done according to the 
Douglass system (Glock, 1937). 

Ages of the mature junipers could not be determined 
because of lobing and erratic growth. 



4 The juniper-pinyon/bitterbrush community characteristic of M-l, near the southern end of Chapin Mesa, at 6,650 feet elevation. 
The 30-foot anemometer support indicates the stunted nature of the trees, their height ranging from 15 to 20 feet. Note the paucity of 
the understory. 



25 



•$. 






m 



m, *-^"-i«a»wff&s*'" 



.^•a^je?****^. 












« -:".-. 









iw-*t 






CHAPTER 3 






description of the stands 



LOWEST MESA-TOP SITE, M-l 

This site was near the south end of Chapin Mesa, about 
5 miles from park headquarters (fig. 1). The lowest of 
the mesa-top sites, at 6,650-foot elevation, M-l was on a 
broad, level ridgetop flanked by two shallow washes that 
empty into the 1,000-foot deep Mancos River canyon 
about y 4 mile away. 

The vegetation is a juniper-pinyon/bitterbrush wood- 
land with sparse herbs (fig. 4). Ephemeral spring flowers 
are important in the ground cover. All species observed 
in the stand are listed in table 2; quantitative data on 
trees are given in table 3. Ten of the largest trees were 
300 to 400 years old, with the oldest pith date being 
A.D. 1529. The trees are small and widely spaced, and 
bitterbrush (Purshia tridentata) and black sagebrush 
{Artemisia nova) are common in openings between them. 
Herbs are conspicuous only during the spring and early 
summer growing season. Some of the most common ones 
are mutton grass (Poa fendleriana) , vetch (Astragalus 
wingatanus) , and phlox (Phlox hoodii). 

The soils at the lower elevations of Mesa Verde are 
generally high in calcium carbonate, due in part to the 
nature of the underlying sandstone and in part to low 
rainfall and high temperatures. Even though soils are 
relatively shallow in the M-l area, the ground surface 
is free of rock material. According to Parsons, the soils 
at this site are quite variable in depth as well as texture, 
but the dominant type has been classified as Penrose 
channery loam. Montvale fine sandy loam also occurs 
in small amounts. The soil profile in table 4 is typical of 
the M-l soils. 

The fine texture of the soil plays an important role in 
the relationship of soil moisture to the growth of the 
plant community. As shown in table 5, the storage ca- 
pacity of growth-water in the heavy soils at M-l is 



relatively high, especially when compared to that of the 
soils at most of the other sites. 

Once the soil dries out, however, and this occurs quite 
early in the year, a large amount of water is required to 
moisten the ground to the depth where roots are located. 
Moreover, because of the sparse vegetational cover, even 
a light rain will induce splash erosion of the surface par- 
ticles, causing the pore spaces to clog and subsequent 
rainfall to be largely lost as runoff. Thus, in the coarse to 
fine loamy soils found at M-l, only a small amount of 
the precipitation percolates into the ground ; this is espe- 
cially true during the summer, when rainfall is heavy. 
This phenomenon is shown graphically in figure 15 
(see ch. 4). The autumn frontal storms of 1962 wet the 
soil down to the 12-inch level, whereas the 1963 summer 
thunderstorms were not so effective. 

Data for the atmospheric and soil factors are presented 
in the appendix. Some of the features commonly used by 
ecologists to characterize environments are given in 
table 6. 

There was less precipitation and a greater variation 
between the 2 years of observations at M-l than at the 
other five sites. The highest wind velocity measured was 
30 m.p.h., in October, when a storm was approaching. 
A mantle of snow persisted only from early January to 
early or mid-March. The frost-free period varied from 
166 days in 1962 to 171 days in 1963. This period in each 
year extended from mid-May through October. 

Plant growth began at M-l earlier in the spring than 
at the other mesa-top stands. Several spring perennials, 
Arabis selbyii, Phlox hoodii, and Poa fendleriana, were in 
flower by late March. 

This type of stand is extensive at the lower elevations 
on the southern part of Mesa Verde (Erdman, MS.). 
Evidence from vegetational analyses and from tree-ring 



27 



TABLE 2— LIST OF SPECIES OBSERVED IN THE ENVIRONMENT MEASUREMENT SITES 



Species 



Sites 



Mesa top 



M-l M-2 M-3 



Canyon 



C-l 



C-2 C-3 



TREE LAYER 



Juniperus osteosperma (Torr.) Little. . 

Juniperus scopulorum Sarg 

Pinus edulis Engelm 

Pseudotsuga menziesii (Mirb.) Franco . 



i X 



SHRUB LAYER 

Amelanchier utahensis Koehne 

Artemisia nova A. Nels 

Artemisia tridentata Nutt 

Atriplex canescens (Pursh) Nutt 

Cercocarpus montanus Raf 

Chrysothamnus depressus Nutt 

Chrysothamnus nauseosus (Pall.) Britt 

Chr)sothamnus viscidiflorus (Hook.) Nutt 

Ephedra viridis Coville 

Fendlera rupicola A. Gray 

Gutierrezia sarothrae (Pursh) Britt. & Rusby . . . . 

Philadelphus microphyllus A. Gray 

Purshia tridentata (Pursh) DC 

Quercus gambelii Nutt 

Rhus trilobata Nutt. ex T. & G 

Ribes leptanthum A. Gray 

Stanleya pinnata (Pursh) Britt 

Symphoricarpos oreophilus A. Gray 

Tetradymia canescens DC 

Yucca baccata Torr 



X 
X 
X 
X 



X 
X 



X 
X 



X 
X 
X 



X 

X 
X 
X 

X 

X 

X 
X 



2 X° 



x° 

X 
X 



GRASS AND FORB I 

Agropyron smitthu Rydb 

Bouteloua gracilis (H. B. K.) Lag 

Bromus tectorum L 

Hilaria jamesii (Torr.) Benth 

Koeleria gracilis Pers 

Oryzopsis micrantha (Trin. & Rupr.) Thurb. . . 

Poa agassizensis Boivin & D. Love 

Poa fendleriana (Steud.) Vasey 

Sitanion longifolium J. G. Smith 

Stipa comata Trin. & Rupr 

Achillea lanulosa Nutt 

Amaranthus hybridus L 

Androsace septentrionalis L 

Antennaria dimorpha (Nutt.) T. & G 

Antennaria parvijolia Nutt 

Arabis drummondii A. Gray 

Arabis pulchra M. E. Jones ex S. Wats 

Arabis selbyi Rybd 

Arenaria congesta Nutt. ex T. & G 

Artemisia ludoviciana Nutt 

Aster arenosus Blake 

Astragalus calycosus Torr. ex S. Wats 

Astragalus flexuosus Dougl. ex Hook 

Astragalus lentiginosus Dougl 

Astragalus schmollae C. L. Porter 

Astragalus scopulorum T. C. Porter 

Astragalus wingatanus S. Wats 

Balsamorhiza sagittata (Pursh) Nutt 

Calochortus nuttallii Torr 

Castilleja chromosa A. Nels 

Castilleja linariaefolia Benth. in DC 

Chaenactis douglasii (Hook.) H. & A 

Chenopodium fremontii S. Wats .- 

Claytonia tanceolata Pursh 

Comandra umbellata (L.) Nutt 

Crepis cf. occidentalis Nutt 

Cryptantha bakeri (Greene) Payson 

Cryptantha gracilis Osterhout 

Cymoplerus bulbosus A. Nels 

Cymoplerus purpurascens (A. Gray) M. E. Jones. 

Cymopterus purpureus S. Wats 

Delphinium nelsonii Greene 

Descurainia pinnata (Walt.) Britt 

Draba reptans (Lam.) Fern 

Echinocereus coccineus Engelm 



X 
X 



X 

x° 

X 

x° 



X 
X 



X 
X 



X 



X 



x° 

X 
X 



X 

X 

X 



X 
X 



X 
X 



X 



X 
X 



X 
X 



X 



X 



X 

X 



X 
X 



X 



X 
X 
X 



X 
X 
X 

X 
X 
X 
X 
X 

X 
X 
X 



X 



See footnotes at end of table. 



28 



TABLE 2.— LIST OF SPECIES OBSERVED IN THE ENVIRONMENT MEASUREMENT SITES— Continued 



Species 



Sites 



Mesa top 



M-l M-2 M-3 



Canyon 



C-l C-2 



C-3 



grass and forb layer — continued 



Erigeron divergens T. & G 

Erigeron fiagellaris A. Gray 

Erigeron pumilus Nutt 

Erigeron speciosus (Lindl.) DC 

Eriogonum alatum Torr 

Eriogonum jamesii Benth 

Eriogonum racemosum Nutt 

Eriogonum umbellatum Torr 

Euphorbia fendleri T. & G 

Frasera albomarginata S. Wats 

Fritillaria atropurpurea Nutt 

Galium coloradoense W. F. Wright 

Gilia ophthalmoides Brand 

Haplopappus armerioides (Nutt.) A. Gray 

Haplopappus nuttallii T. & G 

Hymenopappus fdijolius Hook 

Hymenoxys acaulis (Pursh) Parker 

Impomopsis aggregata (Pursh) V. Grant 

Lappula redowskii (Hornem.) Greene 

Lathyrus pauciftorus Fern 

Lepidium monlanum Nutt 

Lesquerella rcctipes Woot. & Standi 

Lithospermum incisum Lehm 

Lithospermum ruderale Dougl. in Lehm 

Lomatium dissectum (Nutt.) Math. & Const 

Lomatium grayi Coult. & Rose 

Lomatium simplex (Nutt.) Macbr 

Lupinus caudatus Kellogg 

Machaer anther a bigelovii (A. Gray) Greene 

Mammillaria vivipara (Nutt.) Haw 

Melilotus officinalis (L.) Lam 

Mertensia fusiformis Greene 

Microsteris humilis (Dougl.) Greene 

Mirabilia multiflora (Torr.) A. Gray 

Moldavica parviflora (Nutt.) Britt 

Oenothera caespitosa Nutt 

Opuntia phaeacantha Engelm. ex Gray 

Opuntia polyacantha Haw 

Pedicularis centranthera A. Gray 

Penstemon bridgesii A. Gray 

Penstemon eatonii A. Gray 

Penstemon linarioides A. Gray 

Penstemon strictus Benth 

Petradoria pumila (Nutt.) Greene 

Phacelia heterophylla Pursh 

Phlox hoodii Richardson 

Phlox longifolia Nutt 

Physaria australis (Payson) Rollins 

Polygonum sawatchense Small 

Portulaca oleracea L 

Sclerocactus whipplei (Engelm. & Bigel.) Britt & Rose. 

Senecio multilobatus T. & G. ex A. Gray 

Sisymbrium linijolium Nutt 

Solidago sparsiflora A. Gray 

Sphaeralcea coccinea (Pursh) Rydb 

Sphaeralcea parvijolia A. Nels 

Streplanthus cordatus Nutt. ex T. & G 

Taraxacum laevigatum (Willd.) DC 

Townsendia incana Nutt 

Zygndenus venenosus S. Wats 



X 
X 



X 
X 
X 
X 



X 



X 



X 
X 



X 
X 



X 
X 
X 



X 
X 



X 
X 



X 
X 

x c 



X 
X 



X 
X 



x° 



x 



x 

x° 

x 

x 

X 



x° 



X 
X 



x° 

X 

x° 



x 



X 

X 



X 
X 



X 



X 



X 
X 



X 



X 
X 



X 



X 
X 



X 



X 

X 



X 
X 



X 

X 



X 
X 



X 
X 



X 
X 

X 



X 
X 



1 Boldface X indicates species dominant within the stand. 

2 X° indicates species occurs in both the oak thickets and the sagebrush openings at M-3; those restricted to the thickets are Quercus gambelii, Lathyrus pauci- 
ftorus. Ligusticum porteri, and Fhaceliaheterophylla. 



studies indicates that the stand has been relatively un- 
disturbed during the past 400 years and is probably 
climax; that is, a steady-state condition in which no 
further directional change in vegetation takes place under 
prevailing environmental conditions (Hanson and 
Churchill, 1961, p. 159). However, the present-day 



proportion of seedlings of the two tree species suggests 
that some change may be in progress. Among the mature 
trees, juniper is dominant over pine, but there are more 
pine than juniper seedlings. This combination of stand 
characteristics may indicate that pine seedlings are more 
successful than juniper in getting established but their 



29 



TABLE 3— TREE DATA AT M-l 

A. Point quarter analysis based on 10 points 





Number 
of trees 


Average 

distance, 

feet 


Total 
basal 
area, 
square 
inches 


Average 

B.A./ 
diameter 


Density 
trees/acre 


Relative — 


Impor- 


Species 


Density 

(%) 


Fre- 
quency 

(%) 


Domi- 
nance 

(%) 


tance 
value 


Pinus edulis .... 


22 
18 




645 
1,493 


29/6 
83/10.5 


156 
127 


55 
45 


50 
50 


30.2 
69.8 


135. 2 


Juniperus osteosperma 


164. 8 






Total 


40 


12.4 


2, 138 


54/8 


283 


100 


100 


100.0 


300.0 







B. Pinyon-juniper reproduction based on number of individuals 
that occurred within ten 4 x 50-foot belt transects 



Species 


Number of — 


Total 




Seedlings 


Saplings 


Trees 






24 
12 


22 
3 


10 
11 


56 


Juniperus osteosperma 


26 



TABLE 4.— SOIL PROFILE UNDERLYING THE M-l 
JUNIPER-PINYON/BITTERBUSH STAND* 



Description 



survival rate is lower, so that the overall proportions are 
constant. Or it is possible that the present regional climate 
may be favoring a subtle shift toward pine dominance 
(Erdman, MS.). There are differences in the germination 
characteristics of the two species. Pinyon germinates as 
soon as optimum moisture and temperature conditions 
occur (Meagher, 1943), whereas juniper requires ex- 
posure to low temperatures that occur only in winter 
( Johnsen, 1 959) . Consequently, one might expect to find 
more pine seedlings, at least in some seasons. Unfor- 
tunately, there are no data on seedling survival. 

The occurrence of bitterbrush on these heavy soils 
seems to be an exception to recent findings relating to 
the ecology of this species. Nord (1959, p. 2) states that 
in California this shrub does not generally develop where 
the soil is calcareous within 3 feet of the surface and is 
either imperfectly or poorly drained. 

Bitterbrush, so common in this stand-type, is un- 
doubtedly an important factor in the abundance of deer, 
as it is one of their favorite browse plants. 



Horizon 


Depth, 
inches 


A, 


0-3 


C c al 


3-6 


C c a2 


6-11 


c 


11-17 


R 


17 + 



Brown ( 10YR, 5/3 dry) to dark brown ( 10YR 
3/3 moist) channery loam; weak fine platy 
structure, breaking to moderate very fine 
granular; consistence soft dry and friable 
moist ; many fine roots and pores ; about 20 
percent sandstone and shale channery; 
strongly calcareous; lower boundary clear 
and smooth. 

Pale brown (10YR 6/3 dry) to dark brown 
( 10YR 4/3 moist) channery loam; moderate 
fine granular structure; consistence slightly 
hard dry and friable moist ; many fine roots 
and root casts; approximately 25 percent 
sandstone and shale channery; some small 
chalky concretions; violently calcareous; 
lower boundary gradual and wavy. 

Light yellowish brown (2.5Y 7/3 dry) to 
brown (2.5Y 5/3 moist) channery loam; 
weak coarse subangular blocky structure; 
consistence hard dry and firm moist; some- 
what sticky and plastic when wet; 33 per- 
cent sandstone and shale channery; a few 
very fine patchy clay skins show on rock 
surfaces; few small chalky concretions and 
cicada casts; violently calcareous; lower 
boundary clear and smooth. 

Very pale brown (10YR 7/3 dry) to brown 
(10YR 5/3 moist) light clay loam; massive 
structure; slightly hard dry and firm moist; 
slightly sticky wet; fine roots somewhat 
matted between sandstone fragments; ap- 
proximately 50 percent sandstone and shale 
channery; strongly calcareous; lower 
boundary clear and smooth. 

Interbedded sandstone and shale with nu- 
merous tongues of overlying horizon extend- 
ing into cracks in rock. 



'Soil classified as Penrose channery loam. 



TABLE 5.— SOIL MOISTURE CONSTANTS 


IN PERCENT DRY WEIGHT* 










Moisture constant 


Depth, 
inches 


Sites 




M-l 


M-2 


M-3 


C-l 


C-2 


C-3 


Field capacity 


2 

6 

12 

2 

6 

12 

2 

6 

12 


15.0 
19.6 
20.4 

8. 1 
11.6 
12.4 

7.0 
7.9 
8.0 


12.5 
20.0 
16.7 

7. 1 

10.6 

9.3 

5.5 
9.5 
7.4 


12. 1 
14.0 


17.2 
18.6 


7.5 
5.6 
5.7 

4.3 
3. 1 
3.5 

3.2 
2.5 
2.2 


9. 1 




11.4 


Permanent wilting percent 


7.2 
8.9 


10. 1 
10. 1 


5.0 




6.3 


Storage capacity of growth-water 


4.9 
5.2 


7. 1 
8.5 


4. 1 

5. 1 



•Based on triplicate samples and determined by the moisture tension method. 



30 



MIDDLE MESA-TOP SITE, M-2 

The M-2 site was selected as representative of a type 
of stand that occurs about midway between the northern 
and southern extremities of Chapin Mesa. It was at 
7,150 feet elevation, about 1 mile north of park head- 
quarters and within one-half mile of the Weather Bureau 
station. Instruments were placed in a clearing that had 
served as a dirt tennis court between 1937 and 1942 
(fig. 5). 

The vegetation is a pinyon-juniper/mutton grass com- 
munity in which trees and grass are conspicuous and 
dominant, while the shrubs common in other parts of 
Mesa Verde are absent from most stands of this type 
(fig. 6) . Mutton grass (Poa fendleriana) is the understory 



dominant, but the swordlike leaves of yucca ( Yucca 
baccatd) occasionally break the monotony of the pre- 
dominantly tree-grass landscape. There are fewer plant 
species in this stand than in any of the others studied. 
Data on the two species of trees are given in table 7. The 
trees are the largest and the vegetation is the most dense 
of the six stands investigated. Trees are up to 30 feet tall, 
about twice as high as those at M-l, and the largest pine 
and juniper were 17 and 26 inches in diameter, respec- 
tively. The 10 largest pinyon trees were an average of 265 
years old, the oldest being 362 years old (pith date, 
A.D. 1601). These data illustrate the problem of esti- 
mating age from size: a 16-inch-diameter tree was 320 
years old, whereas a 17-inch neighbor Was almost 100 
years younger. 



6 The pinyon-juniper/mutton grass community characteristic of M-2. Mutton grass and broad-leafed yucca are the only conspicuous 
understory plants. The forest here attains a height of about 35 feet, the maximum height on Mesa Verde. 




31 



The surface soils at M-2 are loams, with underlying 
clay loams, and are part of an extensive soil type found 
at Mesa Verde, probably covering the greatest area on 
the mesa tops at this elevation. As can be seen from table 
8, the upper 3 feet of the profile are noncalcareous, or 
only slightly calcareous, and consist of an older soil 
buried by water-deposited and eolian sediments of 
uniform texture. This soil has been classified as Witt 
loam, although at M-2 it is somewhat less well developed 
and the underlying sandstone bedrock occurs only 4 feet 
below the surface. The profile at the type location on 
Chapin Mesa is nearly 10 feet deep, and similar soils at 
pithouse excavations rest on the Cliff House sandstone 
at depths ranging from 4 to 15 feet (Roberts, MS.). 
The soil moisture constants for M-2 are given in table 5. 



The high silt and clay content of the soil probably 
favors establishment of grasses over the deeper-rooted 
shrubs, because fine-textured soils tend to retard root 
penetration. The shrubby plants on Mesa Verde are 
generally most abundant on the shallower soils along 
the mesa rims, in the coarse soils of the canyon talus 
slopes, or on the narrow ridges to the north. 

Environment data are given in table 6 and the ap- 
pendix. The maximum wind gust measured was 36 
m.p.h. A comparison of the M-2 data with that from the 
Weather Bureau station is made in Chapter 4 . 

One important finding is the quantitative effect of 
cloudiness on the amount of solar radiation that reaches 
the earth's surface. The influx of solar radiation was 644 
gm. cal./cm. 2 /day in August of 1962, a month which 



7 M-3, on the North Rim, at 8,575 feet elevation, looking south to Mesa Verde tableland, in late 




TABLE 6.— SOME CLIMATIC FACTORS OF THE MESA-TOP SITES 



Factor 



Air temperature (in degrees Farenheit' 
January: 

Maximum 

Mean maximum 

Minimum 

Mean minimum 

Mean 

July: 

Maximum 

Mean maximum 

Minimum 

Mean minimum 

Mean 

Annual : 

Maximum 

Month 

Mean maximum 

Minimum 

Month 

Mean minimum 

Mean 

Frost-free period, days 

Last freeze in spring 

First freeze in autumn 

Relative humidity (in percentage) : 

Lowest 

Month 

Lowest monthly mean 

Month 

Annual mean 

Precipitation (inches) : 
Monthly total: 

Highest 

Month 

Lowest 

Month 

Annual total 

Wind velocity (in miles per hour) : 
Monthly mean: 

Highest 

Month 

Lowest 

Month 

Annual mean 



1962 



M-l 



46 
37 
-2 
13 
25 

97 
89 
46 
56 
73 

98 

Aug. 

64 

-3 

Feb. 

36 

50 

166 

! May 

Nov. 

1 
May 

22 
June 

43 



2.38 
Oct. 
0.09 
June 
9. 17 



7.0 
May 

4.9 
Dec. 

6.0 



M-2 



52 

38 

-11 

13 
26 

91 
84 
48 
54 
69 

94 

Aug. 

62 

-11 

Jan. 

35 

49 

161 

28 May 

6 Nov. 

5 
May 

36 
June 

53 



2.74 
Oct. 
0.20 
June 
15.80 



6.0 
Apr. 

4. 1 
Dec. 

5.0 



M-3 



50 

31 

-5 

16 

24 

84 
77 
47 
55 
66 

88 

Aug. 

54 

-5 

Jan. 

36 

45 

162 

28 May 

7 Nov. 

9 
May 

35 
June 

51 



2.94 
Oct. 
0.39 
Apr. 
18.86 



12.3 

Jan. 

8.2 

Dec. 

10.3 



1963 



M- 



44 

34 

-23 

11 

22 

97 
91 
52 
59 
75 

97 

July 

64 

-23 

Jan. 

37 

50 

171 

12 May 

31 Oct. 

4 
Apr. 

29 
May 

50 



3.96 
Aug. 
0.02 
June 
13.88 



7.3 
Apr. 

4.4 
Jan. 

5.9 



M-2 



44 

32 

-26 

8 

20 

93 
86 
50 
56 
71 

93 

July 

61 

-26 

Jan. 

34 

48 

171 

12 May 

31 Oct. 



May 
33 

May 
52 



4.54 
Aug. 
0.07 
June 
15.04 



6.5 
Apr. 

4. 1 
Dec. 

5.3 



M-3 



44 
30 
-20 
15 
23 

86 
79 
50 
58 
68 

86 

July 

55 

-20 

Jan. 

37 

46 

171 

12 May 

31 Oct. 

13 
Nov. 

36 
May 

54 



7.62 
Aug. 
0.07 
June 
18.81 



10. 7 
Apr. 

7.5 
Oct. 

9. 1 



TABLE 7.— TREE DATA AT M-2 

A. Point quarter analysis based on 10 points 





Number 
of trees 


Average 

distance, 

feet 


Total 
basal 
area, 
square 
inches 


Average 

B.A./ 
diameter 


Density 
trees/acre 


Relative — 


Impor- 


Species 


Density 
(%) 


Fre- 
quency 

(%) 


Domi- 
nance 

(%) 


tance 
value 


Pinus edulis 


30 
10 




1,273 
883 


42/ 7.5 
88/10.5 


270 

90 


75 
25 


58.8 

41.2 


59 
41 


192.8 




107.2 






Total 


40 


11 


2, 156 


54/ 8.5 


360 


100 


100.0 


100 


300.0 



B. Pinyon-juniper reproduction based on number of individuals 
that occurred within ten 4 x 50-foot belt transects 



Species 


Number of — 


Total 


Seedlings 


Saplings 


Trees 




Pinus edulis 


44 
19 


15 
13 


31 
6 


90 


Juniperus osteosperma. . 


38 



had relatively little cloudiness, and it dropped to 514 
( a 20-percent decrease) in August of 1963, a period of 
considerable cloudiness. 

The frost-free period at M-2, lasting from the latter 
part of May through October, was 161 days in 1962 and 
171 days in 1963. It is interesting that in 1963 the frost- 
free season was the same at both M-l and M-2, although 
there is an elevational difference of 500 feet between the 
sites. Snow covered the ground from mid-December to 



271-475 0-69— 3 



33 




8 A black sagebrush-grass community typical of the openings in the mountain brush zone near M— 3. In addition to several pinyon 
trees (one at left), many seedlings and saplings have become established here. Oak thicket at right. 



the latter part of March during the winters of 1961-62 
and 1962-63. 

Flowering of the early perennials began in April of 
1963, several weeks later than at M-l. 

The total character of this forest stand suggests that 
the site provides near optimum growing conditions for 
both pinyon and juniper. This stand type is an important 
climax ecosystem on the mesa, because it occurs on the 
broad mesa tops in an altitudinal belt across the entire 
Mesa Verde landscape where there is a thick mantle of 
soil. It is a relatively tall, dense forest compared to the 
M-l type and those in most other parts of the pinyon- 
juniper climax region of the Southwest, and it thereby 
gives ecological uniqueness to Mesa Verde. 



HIGHEST MESA-TOP SITE, M-3 

The M-3 site (fig. 7) was located at Park Point, an 
8,575-foot ridge that is the highest point in Mesa Verde. 
This unique setting, providing a spectacular view of the 
surrounding country, made it our windiest site. As 
shown in figure 1 , this site was on the upper escarpment, 
or North Rim, of Mesa Verde, about 5 miles north of 
and 1,500 feet higher than park headquarters and the 
area of the M-2 site. 

The mountain brush zone so prevalent along the 
North Rim is really a patchwork of dense thickets of oak 
and serviceberry, interspersed with openings dominated 
by black sagebrush. Within this patchwork many coni- 



34 




9 An oak thicket in the mountain brush vegetation near M-3. This thicket, about 10 feet tall, recovered after a fire swept over the 
ridge in the mid- 19th century. The major understory species are mutton grass and snowberry. 



fers are gradually becoming established. These are pin- 
yon, primarily, and some junipers (Juniperus osteosperma 
and J. scopulorum) and Douglas-fir {Pseudotsuga menziesii). 

The vegetation of the openings consists of a large 
number of species, and the foliage cover is extensive. 
Black sagebrush is the dominant species in the commu- 
nity, but a few trees and several saplings and seedlings of 
pinyon are established in the sample opening. Black 
sagebrush is a long-lasting successional dominant like 
big sagebrush, but it seems to be better adapted to 
shallow soils than the latter. At present, it covers the 
roadbeds along the North Rim that were abandoned in 
the early 1930's. 

Because the study area is a complex of shrub stands, 



rather than being a continuous forest as in the other 
areas, the vegetation data consist only of a list of plants 
(table 2) present in the two types of local stands — in 
other words, a black sagebrush opening (fig. 8) and 
an oak thicket (fig. 9). 

Soils at M-3 (table 9) are classified as Mughouse 
stony loam. The Mughouse series includes well-drained, 
noncalcareous Brown soils which are developing in 
residual materials derived from the underlying sandstone 
and interbedded shales. These are the typical soils of the 
upland hills and ridges along the North Rim. The soils 
at Park Point are somewhat darker colored than average 
and a hint of A 2 horizonation may be found under the 
older stands of oak brush. Soil depth is quite variable, 

CLEMSON UNIVEI 
DOCUMENT 



ITY LIBRARY 
DEPT. 



TABLE 8 —SOIL PROFILE UNDERLYING M-2 PIN YON- 
JUNIPER/MUTTON GRASS STAND* 



Horizon Depth, 

inches 



A, 



B, 



B 2 it 



A, h 



0-2 



2-5 



5-14 



14-22 



22-34 



34-43 



Description 



R, 



43-47 



47 



Brown (7.5YR 5/3 dry) to dark brown (7.5YR 
4/3 moist) loam; weak to moderate medium 
platy breaking to moderate very fine 
granular structure; consistence soft dry, 
and very friable moist; noncalcareous; 
lower boundary clear and smooth. 

Reddish brown (5.0YR 5/4 dry) to (5.0YR 
4/4 moist) clay loam; moderate coarse 
subangular blocky structure breaking to 
moderate medium and fine subangular 
blocks; consistence hard dry and very 
friable moist; thin patchy clay film on peds; 
very many fine pores; noncalcareous; 
lower boundary clear and smooth. 

Light reddish brown (5.0YR 6/4 dry) to 
reddish brown (5.0YR 4/4 moist) clay 
loam; weak medium prismatic structure 
breaking to moderate medium subangular 
blocks; consistence very hard dry and 
friable moist; thin almost continuous clay 
skins; noncalcareous; lower boundary clear 
and smooth. 

Light brown (7.5YR 6/4 dry) to dark brown 
(7.5YR 4/4 moist) light clay loam; weak 
medium prismatic structure breaking to 
moderate medium subangular blocky struc- 
ture ; consistence very hard dry and friable 
moist; calcareous in spots and patchy films 
on outer surface of soil peds; lower boundary 
gradual and smooth. 

Light reddish brown (5.0YR 6/4 dry) to 
reddish brown (5.0YR 4/4 moist) clay 
loam; moderate to strong medium prismatic 
structure breaking to moderate or stronger 
medium angular blocky structure ; con- 
tinuous clay films; consistence extremely 
hard dry and friable moist; very many fine 
pores; chalky spots and lime films on out- 
side of soil peds with some disseminated 
lime; lower boundary gradual and smooth. 

Light reddish brown (5.0YR 6/4 dry) to 
reddish brown (5.0YR 4/4 moist) clay 
loam; weak medium prismatic structure 
breaking to weak medium subangular 
blocky structure; thin patchy clay films; 
chalky spots with films and disseminated 
lime ; lower boundary gradual and wavy. 

Pink (7.5YR 7/4 dry) to brown (7.5YR 5/4 
moist) loam; massive structure; consistence 
very hard dry and friable moist; almost 
caliche; lower boundary abrupt and 
smooth. 

Sandstone. 



"Soil classified as Witt loam. 

ranging from 18 inches for the weather station profile 
(table 9) to 43 inches in the opening shown in figure 8. 
This, however, approximates the range in depth to bed- 
rock for the series (20 to 40 inches). A considerable 
portion of the station site is covered by a pavement of 
sandstone slabs and channery. The profile in table 9 was 
described from the station site, where the ridge slopes 
south from 5 to 10 percent. Under the oak thickets there 
would be a thicker A[ horizon with a deep litter cover. 

In spite of the relatively low storage capacity of growth 
water in these soils, their shallow depth and heavy charge 
of rock fragments probably induce quite a favorable 
moisture regime. 

The large amount of coarse rock and gravel in these 
soils creates more pore space and increases their permea- 



TABLE 9.— SOIL PROFILE UNDERLYING M-3 MOUN- 
TAIN BRUSH VEGETATION* 



Horizon 



Depth, 
inches 



A, 



B 2t 



R 



0-4 



4-8 



8-13 



13-18 



Description 



18 + 



Gray brown (10YR 5/2 dry) to very dark 
gray brown (10YR 3/2 moist) stony loam; 
strong very fine granular structure ; con- 
sistence soft dry and very friable moist; 
approximately 25 percent sandstone chan- 
nery and stone; noncalcareous; lower 
boundary clear and smooth. 

Brown ( 10YR 5/3 dry) to dark brown ( 10YR 
3/3 moist) stony clay loam; moderate to 
strong fine angular blocky structure ; hard 
dry and friable moist; thin patchy clay 
films on faces of soil peds and on some of the 
sandstone; approximately 50 percent of 
horizon is sandstone channery and stone; 
noncalcareous; lower boundary clear and 
and smooth. 

Light olive brown (2.5Y 5/3 dry) to olive 
brown (2.5Y 4/3 moist) stony heavy clay 
loam; strong fine angular blocky structure; 
extremely hard dry and very firm moist; 
thin nearly continuous clay skins on surfaces 
of soil peds and sandstone rock; approxi- 
mately 50 percent sandstone rock and chan- 
nery; noncalcareous; lower boundary grad- 
ual and smooth. 

Variegated colors ranging from light brown- 
ish grav (2.5Y 6/2 dry) and light olive brown 
(2.5Y 5/4 dry) to grayish brown (2.5Y 4/2 
moist) and olive brown (2.5Y 5/5 moist) 
clay loam extremely hard dry and firm 
moist; thin patchy clay films on soil peds 
and rock surfaces; approximately 50 per- 
cent sandstone flags and channery; non- 
calcareous; lower boundary clear and 
smooth. 

Sandstone and interbedded clay shale with 
numerous tongues of overlying horizon filling 
cracks in bedrock. 



•Soil classified as Mughouse stony loam. 

bility to rainfall. In addition, much of the underlying 
parent material is an unconsolidated, weakly cemented 
residuum which allows deeper wetting. Thus the under- 
lying bedrock may be an important source of moisture, 
acting as a temporary reservoir. These coarse-textured 
soils also favor root penetration. 

One rarely visits the Park Point ridge without expe- 
riencing a conspicuous feature of this site — strong wind. 
Wind velocities at the Park Point station were almost 
twice those measured at the other stations, and they 
seem to be less patterned than those occurring at the 
other stations. For reasons we cannot explain, the early 
part of 1962 was exceptionally windy at the North Rim 
site; however this was not the case at the lower ele- 
vations (fig. 19). 

Although gusts of wind up to 40 m.p.h., were recorded 
at M-3, little is known about their duration or frequency. 
As Daubenmire (1959, p. 269) stresses, mean velocities 
for long intervals of time can be very misleading; winds 
of gale proportions may blow for a few minutes, yet not 
be indicated in the weekly or monthly record. 

Wind has an indirect bearing on the precipitation 
data at M-3. Measurement of precipitation is difficult 
at any site, but where wind velocities are high, as at 
Park Point, the difficulties are compounded. According 



36 




10 The Navajo Canyon setting of the canyon-bottom and slope sites, looking north 



to Conrad and Pollak (1950, pp. 14-15), "the amount 
of water or snow collected in the ordinary gage depends, 
to a certain degree, upon the wind velocity and upon 
the resistance offered by the air to the particles of pre- 
cipitation. The stronger the wind and the greater the 
air resistance, the smaller is the amount caught in the 
gage compared with that collected under otherwise 
similar conditions during absolute calm." Daubenmire 
(1959, p. 92) points out that precipitation gages with 
large diameters tend to deflect wind upward as it strikes 
the instrument, a phenomenon which may reduce the 
actual amount of moisture by more than half. Because 
snow would be deflected even more easily than rain, the 



winter record is probably in greater error than the 
summer one. Thus it is necessary to take into account 
the effect of wind on the overall moisture record at M-3. 

One important effect of wind on plants is to increase 
transpiration. Our evaporation data give information on 
this point. Evaporation at M-3 during summer months 
was the highest of all sites measured, even though the 
air temperatures were comparatively low. 

Wind also has a significant effect on the length of the 
frost-free period. Since M-3 is higher than the other 
mesa-top sites, one would expect it to have a shorter 
frost-free season. But this was not the case. In 1963, 
this period was 171 days, identical to that of the other 



37 



mesa-top stations. In 1962, it was 162 days, again very 
similar to the other sites. According to Geiger (1957, 
p. 110), higher wind velocity means increased convec- 
tion, and increased convection results in decreased tem- 
perature gradients. Consequently, temperatures are lower 
during the day and higher at night. It is the moderating 
effect of wind at night that is responsible for the extended 
frost-free period at this site. 

The similarity in the frost-free periods between sites 
does not mean that the growing seasons of plants are 
the same at all the sites. Actually, plant growth begins 
long before the last spring frost. In the spring of 1963, 
flowering of the indigenous plants at M-3 did not begin 
until late April, 2 to 3 weeks later than at M-2. The 
delay in growth at M-3 may have been due to a late 
snow cover and to a lag in the "warming of the soil. 
Snow cover, though variable because of drifting, per- 
sisted from late November through March. The soil 
temperature records for 1963 show that substantial thaw- 
ing and heating of the ground did not occur before 
May. Mutton grass, which began flowering early in April 
at the lower elevations, did not flower until the first 
week in May at M-3. Similarly, serviceberry started to 
flower at the canyon stations the last week of April, but 
did not begin flowering along the North Rim until a 
month later. In general, therefore, a 3- to 4-week delay 
in flowering was evident between the northern and 
southern ends of Mesa Verde. 

The M-3 vegetation is undergoing stages of changes 
from pioneer stands that developed after fires to the 
relatively stable climax cover of a pinyon and juniper 
forest. Burned stumps and charcoal throughout the area 
indicate that only small islands of the landscape have 
escaped burning. 

Through the use of dendrochronological techniques, 
both on the burned specimens and modern increment 
cores from the present stand of scattered trees, it appears 
that a fire swept over the ridge about 1840. An earlier 
fire may have occurred in the 1600's, as the oldest pith 
date from the sample collection is 1710, with several more 
specimens giving approximately the same date. More- 
over, these trees were relatively young when they burned. 

Shrubs have fared better because they are able to 
produce new shoots from adventitious buds on the root 
crowns that survive fire. The local trees lack this regen- 
erative capacity. Trees are now reproducing from seed 
throughout the area, so we do not doubt that forest will 
eventually replace the shrublands if fires are suppressed. 

That the M-3 shrub vegetation is successional does not 
in itself indicate the area has soils or atmospheric factors 
different from the other stands we studied. In the ab- 
sence of a true climax stand, however, we are unable to 
characterize the type in detail. The lushness of the shrubs 
and the more favorable water complex suggest that 
the forest would be more mesophytic, except on exposed 
sites where wind would produce more arid conditions. 



CANYON- BOTTOM SITE, C-2 

The canyon sites were in Navajo Canyon (figs. 1 and 
10), about one-half mile west of park headquarters and 
1 y 2 miles southwest of the M-2 site. The canyon-bottom 
site was on an alluvial terrace at 6,382-foot elevation, 
about 800 feet lower than the mesa top. The terrace is a 
remnant of an alluvial deposit that has been dissected 
by the intermittent stream. 

The vegetation of C-2 (fig. 1 1) is almost a pure stand 
of big sagebrush, averaging 5 feet high. Sagebrush covers 
over 75 percent of the stand, and cheatgrass (Bromus 
tectorum) is the only other plant in abundance. Additional 
herbs present are listed in table 2. This is a climax stand, 
and such stands of big sagebrush occur on all the alluvial 
terraces in the Mesa Verde canyons. On the mesa tops, 
sagebrush is successional, but in the canyon bottoms it 
is better adapted to the deep alluvial soils than other 
species and is able to maintain its dominance. 

The boundary between the sagebrush community and 
the adjacent pinyon-juniper forest on the canyon slopes 
is very pronounced (figs. 10 and 11), the line occurring 
where the coarse colluvium of the talus abuts the alluvial 
sediments of the terraces. The soils on these terraces are 
azonal; that is, the profile has an A, C horizon sequence 
(table 10). These soils were developed on a flood plain 
or low terrace formed over the bedrock of the rather nar- 
row canyon bottom. Subsequent erosional processes have 
cut the present intermittent stream channel, which dis- 
sects the old flood plain. The soil at the C-2 station is 
classified as Bankard fine sandy loam. It is a deep, coarse- 
textured, alluvial soil developing from wind and water- 
sorted sediments derived from the Mesaverde group. 

The presence of charcoal fragments, described as 
"many dark flakes of carbonaceous material" in the Aj 
horizon, is probably the result of a fire that occurred in 

TABLE 10.— SOIL PROFILE UNDERLYING C-2 BIG 
SAGEBRUSH/CHEATGRASS STAND* 



Description 



Brown (10YR 5/3 dry) to dark brown (10YR 
3/3 moist) loamy fine sand; soft dry, very 
friable moist; weak platy breaking to weak 
very fine granular structure ; many dark 
flakes of carbonaceous material; noncal- 
careous; lower boundary clear and smooth. 

Light brownish gray (10YR 6/2 dry) to dark 
gray brown (10YR 4/2 moist) very fine 
sand; single grained; soft dry, very friable 
moist; noncalcareous; lower boundary 
gradual and smooth. 

Light brownish gray (10YR 6/2 dry) to dark 
gray brown (10YR 4/2 moist) very fine 
sand ; single grained ; soft dry, very friable 
moist; weakly calcareous; lower boundary 
gradual and smooth. 

Light brownish gray (10YR 6/2 dry) to dark 
gray brown (10YR 4/2 moist) moderate to 
very fine sands ; massive ; soft dry, very 
friable moist ; calcareous. 



•Soil classified as Bankard lino sandy loam. 



Horizon 


Depth, 
inches 


A, 


0-4 


c, 


4-32 


C, 


32-54 


Q, 


54-60 



38 




1 1 C-2, on an alluvial terrace in the bottom of Navajo Canyon, at 6,382 feet elevation. The big sagebrush community is r< 
the sandy soil of the terrace. In the background, upper center, is the environment station for the east-northeast-facing slope. 



stricted to 



the station area. Several charred juniper trees were 
found near the anemometer support. 

The soil moisture coefficients listed in table 5 are 
indicative of the relatively light soil prevalent at C-2. 
The storage capacity of this soil is very low, a feature 
detrimental to the growth of shallow-rooted plants. 

Two features of the C-2 site — cold night temperatures 
throughout the year and deep soil — make its growth 
regime similar to that found in the Saeebrush Desert of 
the Great Basin, a region where the frost-free season is 
very short and where frosts occur almost every night in 
fall, winter, and spring (Costing, 1956, p. 321). The 
pronounced differences in temperature between the 



canyon floor and the other stands are discussed on 
page 48. Other environmental data are in table 11 and 
the appendix. 

Benson (1957, p. 617), in discussing Cold Desert vege- 
tation, states that the typical sagebrush community has a 
higher water requirement and is therefore restricted to 
better and usually deeper soils. The general limitation of 
big sagebrush to this type of site may be due more to its 
deep root system which can tap water sources not avail- 
able to many other shallower rooted plants — it is better 
adapted to these sandy, well-drained soils. Roberts (MS.), 
in his study of the soils of Wetherill Mesa, says that the 
occurrence of big sagebrush is closely correlated with 



39 



TABLE 11.— SOME CLIMATIC FACTORS OF THE CANYON SITES 



Factor 



Air temperature (in degrees Fahrenheit): 
January: 

Maximum 

Mean maximum 

Minimum 

Mean minimum 

Mean 

July: 

Maximum 

Mean maximum 

Minimum 

Mean minimum 

Mean 

Annual: 

Minimum 

Month 

Mean maximum 

Minimum 

Month 

Mean minimum 

Mean 

Frost-free period, days 

Last freeze in spring 

First freeze in autumn 

Relative humidity (in percentage): 

Lowest 

Month 

Lowest monthly mean 

Month 

Annual mean 

Precipitation (inches): 
Monthly total: 

Highest 

Month 

Lowest 

Month 

Annual total 

Wind velocity (in miles per hour): 
Monthly mean: 

Highest 

Month 

Lowest 

Month 

Annual mean 



1962 



C-l 



48 
39 
-2 
16 
28 

95 
89 
51 

55 
72 

97 
Aug. 

65 

-2 

Jan. 

37 

51 

168 

May 

Nov. 

4 

May 
37 

May 
52 



C-2 



47 

38 

-7 

8 

23 

97 
90 
42 
50 
70 

98 

Aug. 

65 

-8 

Feb. 

30 

47 

102 

29 May 

9 Sept. 

4 
May 

42 
Aug. 

57 



2.52 
Oct. 
0.18 
June 
13.93 



3.1 
May 

1.3 
Dec. 

2.2 



C-3 



48 
38 

-2 
16 
27 

95 
90 

54 
57 
74 

100 

Aug. 

64 

-2 

Jan. 

37 

51 

173 

18 May 

8 Nov. 

10 
May 

37 
June 

56 



1963 



C-l 



48 
34 
-20 
10 
22 

98 
92 
54 
59 
75 

98 

July 

65 

-20 

Jan. 

37 

51 

171 

12 May 

31 Oct. 

4 
May 

29 
May 

49 



C-2 



48 

34 

-28 

4 

19 

97 
91 
44 
52 
72 

97 

July 

65 

-28 

Jan. 

31 

48 

123 

1 1 June 

13 Oct. 

8 
May 

45 
June 

59 



4.15 
Aug. 
0.06 
June 
14.52 



3.4 
June 

1.5 
Feb. 

2.2 



C-3 



44 
35 
-19 
12 
24 

102 

92 
54 
59 
75 

102 

July 

64 

-19 

Jan. 

37 

51 

184 

29 Apr. 

31 Oct. 

10 
June 

35 
May 

54 



areas where the roots can have a deep feeding zone with 
relatively high available moisture. 

The most striking climatic phenomenon in the canyons 
is the nocturnal flooding of cold air down the drainage- 
ways, ultimately flowing along the bottom of the canyon. 
This produces a pronounced difference in nighttime air 
temperature and humidity between the canyon bottom 
and the adjacent slopes. A combination of relatively low 
winds at C-2 (see appendix) and its topographic 
setting favors high temperatures during the day and cold 
nocturnal temperatures. The temperatures regime is thus 
marked by a diurnal range exceeded nowhere else in 
the Mesa Verde complex. 

Because of the lower minimum temperatures at C-2, 
the frost-free period is shortened considerably. In 1962, 
it was only 102 days long, lasting from late May until 
early September. The 1963 season was longer (123 
days), extending from mid-June to mid-October. 

The initiation of flowering in the canyon bottom is 
delayed as a result of the short frost-free period and late- 



lying snows. In 1963, Phlox hoodii, one of the first peren- 
nials to flower on the entire mesa, did not bloom at C-2 
until the second week in May; and from the phenological 
observations made throughout the spring, there seemed 
to be little plant development prior to that time. 

The absence of a variety of herbs is probably due to 
suppression under the extensive crown cover of sagebrush 
(Hanson and Churchill, 1961, p. 85) and to competition 
with cheatgrass. The latter is a winter annual that 
germinates in the fall and puts on a burst of growth in 
the spring, when its extensive root system can absorb 
water from the melting snow. Few herbs can compete 
with it in vigor during the early part of the warm season. 

Cheatgrass plays another potentially critical role in the 
ecology of this stand type. The grass dries up as the 
warm season progresses and becomes tinder that ignites 
easily and often sets fire to the sagebrush. Such fires are 
common in the West today, but they are of relatively 
recent origin, since cheatgrass was introduced to North 
America from Europe only in the 19th century. 



40 







-3Rlt f ^iM-Jh . . J '-i.jtfl&l/ A-ST-iz 



12 C-l, on west-southwest-facing talus slope in Navajo Canyon, with instrument shelter visible in lower center, between sandstone 
outcroppings, about 125 feet above the canyon floor. 



SOUTHWEST EXPOSURE CANYON- 
SLOPE SITE, C-l 

This site was 125 feet above the canyon floor, at an ele- 
vation of 6,500 feet. It was halfway up a southwest- 
facing talus slope of 35° (fig. 12). The vegetation is a 
juniper-pinyon community with scattered big sage- 
brush. The trees are small and widely spaced (fig. 13), 
the average distance between them being more than 20 
feet, which is considerably greater than in the other 
stands (table 12). Most of the local shrubs, with the ex- 
ception of oak and fendlerbush, are represented in the 
community. Sagebrush is confined to deep, well-drained 



soils at other sites on the mesa, but on talus slopes it is 
common on the heavy soils associated with shale out- 
croppings. Since there are lenses of shale throughout the 
slope, sagebrush is the characteristic shrub of the stand- 
The other species present are listed in table 2. 

The largest juniper and pinyon were 24 and 14 inches 
in diameter, respectively. The oldest of 10 pines sampled 
was 240 years, and the average for the 10 was 160 years. 
This is the only stand type sampled in which juniper is 
more abundant than pine. 

The soils on the steep canyon slopes are formed partly 
from coarse colluvial-alluvial materials and partly from 
the underlying bedrock. Because several different soils 



271-475 0-69— 4 



41 




13 C— I instrument shelter, at about 0, 500-foot elevation. The soil here is a Sandstone Outcrop-Stonyland Complex, and the vegetation 
is an open juniper-pinyon/big sagebrush community. 



could be recognized and because of the steepness of the 
slope, the general soil type suggested for the southwest- 
facing talus on which C-l is situated is the Mughouse- 
Rock Outcrop Complex. The soil at the site is classified 
as a shallow phase of Mughouse stony loam. It is shal- 
lower, less developed, and somewhat more brown than 
normal, but it fits the series fairly well. 

Developing on interbedded shales and sandstones of 
the Menefee formation, the soil is quite stony, with most 
of its coarse material having come from the more resist- 
ant Cliff House sandstone above. The depth of the soil 
is variable; below the cliffs it is often less than 12 inches 



deep. Many shallow outcroppings of shales and sand- 
stones occur on this broad talus slope. The profile de- 
scription in table 13 is taken from the open area just to 
the right of the shelter in figure 13. 

A contact zone between the Cliff House sandstone and 
the underlying Menefee formation (primarily shales) is 
replete with seeps and springs. Below this point of con- 
tact, moisture from lateral flow of ground water seems 
negligible, at least over much of the canyon slopes. Thus 
the primary source of water for the slope vegetation is 
precipitation, but retention of moisture varies greatly 
where soils are so variable. Where coarse colluvium 



42 




14 C— 3 instrument shelter on the east-northeast-facing talus slope in Navajo Canyon, directly across from C- 
increase in the density of the pinyon-juniper forest and in the abundance of the brush understory. 



There is a decided 



occurs, the interstices between the rocks and boulders 
trap and retain much of the runoff to the advantage of 
the deeper rooted plants. But where the soils are fine 
textured along the shale lenses, porosity and water perme- 
ability are low, even though the water-holding capacity 
(as shown in table 5) is quite high. 

The C-l site represents a segment of the Mesa Verde 
terrain whose climate is controlled by the local topog- 
raphy or, more precisely, by exposure. Facing west- 
southwest, the slope receives more insolation, on an 
annual basis, than any of the other sites. This is espe- 
:ially pronounced during the winter months. (See air 



temperature data in the appendix). As a result, 
daytime temperatures exert the greatest influence on 
the environment. Whereas M-l represents the most arid 
mesa-top environment, C-l, indicative of the more ex- 
posed canyon slopes, is in the more arid part of the 
canyon landscape. 

At C-l, moderate soil temperatures during the winter 
and the southerly exposure favor early spring develop- 
ment of the vegetation. Snow rarely blankets the slope 
for any extended period of time. During the winters 
observed, snow persisted from the latter part of December 
through late January; otherwise, cover was generally 



43 



TABLE 12.— TREE DATA AT C-l 

A. Point quarter analysis based on 10 points 





Number 
of trees 


Average 

distance, 

feet 


Total 
basal 
area, 
square 
inches 


Average 

B.A./ 
diameter 


Density 
trees/acre 


Relative — 


Impor- 


Species 


Density 

(%) 


Frequency 

(%) 


Dominance 
(%) 


tance 
value 




19 
21 




1,031 
2,952 


54/ 8.5 
141/13.5 


51 
56 


47.5 
52.5 


52.6 
47.4 


25.9 
74.1 


126 


Juniperus osteosperma 




174 






Total 


40 


20.2 


3,983 


100/11.5 


107 


100.0 


100.0 


100.0 


300 



B. Pinyon-juniper reproduction based on number of individuals 
that occurred within ten 4 x 50-foot belt transects 



Species 


Number of — 


Total 




Seedlings 


Saplings 


Trees 






5 
2 


5 
9 


5 
6 


15 


Juniperus osteosperma . . 


17 



spotty. All these factors support the conclusions drawn 
from our phenological information: that plant growth 
commences earliest at this site. In 1963, the flowering of 
Phlox hoodii began the third week in March and was 
abundant by the end of the month. This was delayed 
about a week the previous year. Flowering of the shrub 
species, beginning with Amelanchier, also occurred first 
at the C-l site. 

In brief, the environment of the southwest-facing 
canyon slopes is comparable to that along the southern 
part of Mesa Verde, and plant growth is least favorable 
at these locations. Data on the atmospheric factors are 
given in table 1 1 and the appendix. 

TABLE 13.— SOIL PROFILE UNDERLYING C-l 
JUNIPER-PINYON/BIG SAGEBRUSH STAND* 



Horizon 


Depth, 
inches 


Description 


A, 
B2U 

B 2 2t 

R 


0-5 
5-9 

9-21 

21 + 


Gray brown ( 10YR 5/2 dry) to very dark gray 
brown (10YR 3/2 moist) stony loam; 
moderate to strong fine granular structure ; 
consistence soft dry very friable moist; 
many fine roots; approximately 25 percent 
sandstone cobbles and flags; noncalcareous; 
lower boundary clear and smooth. 

Light gray brown ( 10YR 6/2 dry) to dark gray 
brown (10YR 4/2 moist) stony clay loam; 
moderate medium to coarse subangular 
blocky breaking to moderate to strong fine 
angular and subangular blocky structure; 
consistence very hard dry; firm moist; 
very thin patchy clay skins; few fine roots; 
largely concentrated along faces of soil 
peds; rock fragments 25 percent; noncal- 
careous except for small fragments of 
weathered shale; lower boundary gradual 
and wavy. 

Gray brown (2.5Y 5/2 dry) to very dark gray 
brown (2.5Y 3/2 moist) stony clay; weak 
subangular blocky structure extremely hard 
dry, firm moist sticky and plastic wet; thin 
patchy clay skins on peds and rock surfaces; 
25 to 50 percent rock fragments; noncal- 
careous except for fragments of weathered 
shale; lower boundary gradual and wavy 
with stringers of horizon extending down- 
ward into cracks in underlying rocks. 

Interbedded sandstone and shale. 



•Soil classified as Mughouse stony loam. 



NORTHEAST EXPOSURE CANYON- 
SLOPE SITE, C-3 

The northeast exposure site is direcdy across the 
canyon from C-l. Located on a 35° talus slope at an 
elevation of 6,500 feet, C-3 is about 100 feet above the 
canyon floor (fig. 14). 

The pinyon-juniper vegetation is more dense than that 
on the opposite slope, and two additional shrubs, oak 
and fendlerbrush, occur in the stand here (table 14). 
Other species of plants present are listed in table 2. The 
trees averaged 250 years old and the oldest individual 
was just over 260 years. The trees are older on this slope 
than on the opposite, southwest-facing (C-l) slope. This 
might be due to a sampling error, but the same relation- 
ship was found between the trees on the northeast- and 
southwest-facing slopes of Rock Canyon. These observa- 
tions suggest that trees may actually live longer on 
northeasterly exposures. 

The soil at this site is included in the Cliffhouse series, 
although it lacks strongly structured clay characteristic 
of the lower B horizon in this series. It is a moderately 
deep soil developing on the interbedded sandstone and 
shales of the Menefee formation. Cliffhouse soils are 
found primarily on the uplands or mesa tops and are 
not typical of the canyon's talus soils. Soil moisture 
samples and the soil profile described in table 15 were 
taken from a high, sloping bench slightly above the 
the C-3 site. 

In the soil survey of Wetherill Mesa and adjacent 
canyons, the predominant soils of the talus situations 
were of the Mughouse-Rock Outcrop Complex. Since 
soils of the C-l slope in Navajo Canyon are also in this 
category, it is reasonably safe to assume that the soils of 
the C-3 slope, as a whole, fall into the Mughouse series. 

The data for growth-water storage listed in table 5 are 
somewhat conservative, since the nature of the under- 
lying bedrock favors deep penetration and may carry 
some laterally moving water. Cracks in the bedrock also 
serve as moisture storage zones, as evidenced by the 
presence of roots, soil, and clay skins. 

Environment data are presented in table 10 and the 
appendix. The local environment at C-3, like that of 
C-l, is strongly influenced by exposure to solar radiation. 
C-3 has slighdy higher maximum air temperatures than 



44 



TABLE 14.— TREE DATA AT C-3 

A. Point quarter analysis based on 10 points 





Number 
of trees 


Average 

distance, 

feet 


Total 
basal 
area, 
square 
inches 


Average 

B.A./ 
diameter 


Density 
trees/acre 


Relative — 


Impor- 


Species 


Density 

(%) 


Fre- 
quency 

(%) 


Domi- 
nance 

(%) 


tance 
value 


Pinus edulis 


30 
10 




989 
2,754 


33/ 6.5 
275/18.5 


145 
48 


75 

25 


58.8 

41.2 


26.5 
73.5 


160.3 


Juniperus osteosperma 


139 7 






Total 


40 


15 


3,743 


94/11.0 


193 


100 


100.0 


100.0 


300.0 







B. Pinyon-juniper reproduction based on number of individuals 
that occurred within ten 4 x 50-foot belt transects 



Species 


Number of — 


Total 




Seedlings 


Saplings 


Trees 






8 
3 


3 
1 


8 
3 


19 


Juniperus osteosperma . 


7 



C-l, but nocturnal temperatures on the two slopes are 
essentially identical because these temperatures are 
determined by the mass movement of cold air, which is 
independent of slope exposure. 
Slope direction, which affects the duration of snow 

TABLE 15.— SOIL PROFILE UNDERLYING C-3 PINYON- 
JUNIPER/MOUNTAIN BRUSH STAND* 



Description 



Dark brown (7.5YR4/3 dry) to dark brown 
(7.5YR 3/3 moist) fine sandy loam; mod- 
erate to strong very fine granular structure ; 
very friable moist; abundant fine roots; 
approximately 10 percent sandstone frag- 
ments; noncalcareous ; lower boundary 
clear and smooth. 

Gray brown (9YR 5/2 dry) to very dark gray 
brown (9YR 3/2 moist) very fine sandy 
loam; weak coarse subangular blocky 
structure; consistence hard dry, very 
friable moist; many fine roots and pores; 
about 10 to 20 percent sandstone fragments; 
noncalcareous; lower boundary clear and 
smooth. 

Brown (7.5YR 5/4 dry) to dark brown (7.5YR 
3/4 moist) loam or sandy clay loam; weak 
coarse prismatic structure breaking to weak 
to moderate medium subangular structure; 
consistence very hard dry and friable moist ; 
many fine roots and pores; thin patchy 
clay skins; 20 percent sandstone fragments; 
weakly calcareous; lower boundary clear 
and smooth to slightly wavy. 

Pale brown (10YR 6/3 dry) to dark brown 
(10YR 4/3 moist) sandy clay loam; weak 
coarse prismatic structure; consistence 
very hard dry and friable moist; very thin 
very patchy clay skins; about 20 percent 
sandstone fragments; weakly calcareous; 
lower boundary clear and smooth. 

Relatively soft interbedded sandstone and 
shale with roots and soil from above horizon 
extending a few inches into the numerous 
weathering cracks. 



Horizon 


Depth, 
inches 


A, 


0-A 


A 3 


4-11 


8211 


11-16 


B 22 t 


16-21 


R 


21 + 



cover and its relationship to soil moisture during the 
growing season, is probably the most important factor 
controlling the stand vegetation. Although the frost-free 
period at C-3 was similar to that at C-l (173 days in 
1962 and 184 days in 1963), the duration of snow cover 
at the two sites was not the same. The C-3 slope kept a 
mantle of snow for several months, whereas C-l had an 
ephemeral snow cover. In 1963, the late-lying snows 
were probably responsible for the delay in flowering on 
the C-3 slope until early April. The more favorable soil 
moisture conditions may account for the denser vegeta- 
tion on the less-exposed slopes. 

The stand at C-3 is a climax ecological unit whose 
character is influenced strongly by topography and soil. 
The presence of oak and fendlerbush indicates that this 
site is more mesic — that is, relatively more moist — than 
adjacent sites in the canyons and on the mesa top. These 
two shrubs suggest that C-3 is more-like M-3 than any 
of the other sites studied at Mesa Verde. 



'Soil classified as Cliffhouse fine sandy loam. 



45 



CHAPTER 4 



discussion of site interrelations 



Data collected at the six sites were presented in the 
previous section, along with observations on the inter- 
relations of the different ecosystem components. Many 
comparisons of the environmental data can be made. 
The comparisons discussed in this chapter were chosen 
for their relevance to the project's objectives. The annual 
environment data are included in this report (see 
appendix) in order to make them readily available for 
use in other studies. 

SOIL AND VEGETATION RELATION- 
SHIPS OF SELECTED SITES 

A comparison of soil types indicates a similarity among 
the M-3, C-l, and C-3 sites — all are stony loams in the 
Mughouse series. These fine-textured soils are relatively 
shallow, have a large proportion of rock fragments, and 
support woody shrubs. 

The M-l and C-2 sites have azonal soils (lacking a 
natural horizonation) but are otherwise very dissimilar. 
The M-l soils — lithosols — support black sagebrush 
{Artemisia nova), an indicator of shallow soils. The 
alluvium at C-2 supports a dense stand of big sagebrush, 
a shrub best adapted to deep, friable soils. 

The M-2 site is unique in that its soil, a Witt loam, is 
highly developed, as well as deep, and supports a climax 
stand of forest and grass that is generally devoid of 
any woody shrubs. 

Some characteristics of soil moisture, a critical factor 
in any semiarid area such as Mesa Verde, are given in 
figure 15. The annual pattern of soil moisture shows 
similarities as well as differences during the 2 years of 
our study. In both years, moisture from melting snow 
built up in the soil in early spring and then dropped 
rapidly as the dry season came on in late spring. In 1963, 
precipitation in August recharged the soil moisture in a 



way that is probably typical of the area. The year of 
1962, on the other hand, provided an example of an 
extremely dry summer. There was so little precipitation 
that soil moisture remained deficient until fall. 

Comparisons between sites show that moisture was 
deficient at the 6-inch depth for the longest period at 
the southwest exposure site (C-l) and for the shortest 
period in the canyon floor site (C-2). The latter case 
was due to the frozen condition of the ground, which 
persisted well into the spring. 



COMPARISON OF 1962 
WEATHER 



AND 1963 



An important aspect of climate from an ecological 
standpoint are year-to-year variations in weather fac- 
tors. There was little difference between the 2 years of 
our study in annual averages and totals; however there 
were striking differences in the monthly records for these 
years. 

Solar radiation. This was similar in all months of the 
2 years except August, when the daily values were 644 
gm. cal./cm. 2 /day in 1962 and only 514 in 1963. 
The lower value for 1963 resulted from greater cloudi- 
ness, precipitation, and relative humidity — conditions 
that would reduce the amount of solar radiation reaching 
the ground. 

Precipitation. As mentioned earlier, the annual pre- 
cipitation at Mesa Verde averaged 18 inches over the 
past 41 years. The 14 inches in 1962 and 15 inches in 
1963, recorded at the Weather Bureau station, were thus 
somewhat below normal. Total precipitation differed 
very little — about 1 inch during the 2 years of the 
environment program. This was also true of the canyon 
and other mesa-top sites, except for M-l at the lower 



47 



end of Chapin Mesa. There, a difference of almost 5 
inches was recorded (fig. 16). 

The hazards in generalizing about a year's weather 
from such information can be seen in figure 16. Only 
the late spring was dry in 1 963, whereas the entire summer 
was relatively dry in 1962. The effects of such a distri- 
bution of moisture on plants, especially cultigens depend- 
ent upon summer rains, is obvious. 

The extremely wet summer of 1963 deserves further 
comment. Although August is usually the wettest month 
of the year, the Weather Bureau station received twice 
the normal amount in August 1963. Moreover, at the 
M-3 site on Park Point, almost half of the year's precipi- 
tation came during that month! In contrast, in August 
of 1962 the Weather Bureau station received less than 
one-tenth of the average for August. Snowfall in both the 
winters of 1961-62 and 1962-63 was below normal, but 
the former had more snow than the latter. 

Evaporation. At all sites, this was higher in 1962 than 
in 1963. The potential summer evaporation, as measured 
by the atmographs, greatly exceeded the actual yearly 
precipitation. Some summer months had evaporation 
potentials that were about half the yearly precipitation. 

Temperature. Temperature recordings at the Weather 
Bureau station during 1962 and 1963 are shown in table 
1. Air temperature fluctuations at all the environment 
measurement sites were more alike during 1963 than 
during 1962, perhaps because of the greater amount of 
cloudiness and rainfall in 1963. Clouds and moisture 
would tend to reduce the effect of locally modifying 
forces, and thus local conditions would approximate 
regional conditions. 

COMPARISON OF INDIVIDUAL 
FACTORS BETWEEN SITES 

Solar radiation. As one of the major controls of other 
environmental factors, solar radiation was consistently 
higher at M-2 than at C-2 throughout the year. The 
reason for this difference is obvious; when the sun is low 
during the early morning and late afternoon, the canyon 
floor is in the shadow of the upper cliffs of the mesas. 

Although we did not measure this factor on the talus 
slopes, we have studied it from indirect sources because 
of its importance in understanding the local environ- 
ments of the canyons. There are many indications that 
C-l, with its southwest exposure, receives more solar 
radiation than does C-3, on the opposite slope. Although 
the following measurements of incident angles of direct 
sunlight show that the southwest slope receives more 
solar radiation at noon, the actual maximum radiation 
occurs in late morning at the northeast exposure and in 
early afternoon at the southwest exposure. The smaller 
the angle, the more direct the sunlight perpendicular to 
the slope. It is evident that the radiation regimes become 
more alike in summer. 



An effect of the solar radiation load on the two slopes 
can be seen in the temperature differences. The march 
of air temperatures on clear summer and winter days 
(fig. 17) indicates that solar radiation was higher on the 
southwest exposure slope during late autumn and winter, 
whereas the northeast slope received more radiation 
during late spring and summer. We believe that the 
southwest exposure receives more solar radiation on a 
yearly basis, but the northeast slope probably receives 
more during the growing season. The topography and 
orientation of the two sites is such that the sun reaches 
the northeast exposure first during all seasons of the year 
(calculated from Geiger, 1957, p. 221). 

Perhaps the most reliable indicator of solar radiation 
intensities on the two slopes is the persistence of snow; 
snow cover is intermittent on the southwest exposure, 
while it persists most of the winter on the C-3 slope. 

The density of the vegetation is both a result and a 
cause of differences in the amount of solar radiation. If 
both slopes were bare of plants, the southwestern ex- 
posure would receive more total radiation for the year 
and, consequently, it would be less mesic. Since plants 
are present, they tend to produce a more complete cover 
on the more mesic, northeastern exposure. The more 
open vegetation of the southwestern slope thereby 
permits greater heating of the soil and air. 

The effect of clouds on insolation is difficult to de- 
termine. Clear mornings and cloudy afternoons are 
common throughout the summer. A rather complete 
cloud cover in the afternoon would reduce the total daily 
radiation on the southwestern slope more than on the 
northeastern slope because at that time of day solar 
radiation is potentially more direct on the former. 
Scattered cumulus clouds could, however, actually 
increase radiation through reflection. 

Air temperature and cold-air drainage. At all sites, 
minimum air temperatures varied more from day to day 
than did maximum temperatures. Both maximum and 
minimum temperatures varied more in the winter than 
in the summer. 

Early study of our data showed the expected pattern of 
cold-air drainage. Air that becomes colder, and therefore 
more dense due to local cooling, drains downslope and 
accumulates in lowlands. The drainage is most striking 
on clear and calm nights in summer. In order to study 
this phenomenon more intensively, Weather Bureau- 
type maximum and minimum thermometers were 
mounted at shoulder height on the north side of trees in 
small, ventilated shelters. These shelters were established 
at intervals of 50 feet along a transect from the canyon 
floor to the base of the cliff (fig. 18). 

During the summer, cold air builds up to a level less 
than 50 feet deep in the canyon bottom. Above the 50-foot 
level, minimum temperatures are almost isothermal to 
the bottom of the cliff, while the mesa top is as cool as the 
50-foot level. During the day, however, the cold air is 



I,". 




J_ ll III I .1 



.llll.lllll ll, .. I. 



J FMAMJ J ASONDJ FMAMJ J ASOND 



M2 STATION 




J FMAMJ JASONDJ FMAMJ JASOND 



M3 STATION 




CI STATION 




J FMAMJ JASONDJ FMAMJJASOND 




15 Graph showing soil moisture content and precipitation at the six sites in 1962 and 1963. The light hatching indicates available 
moisture, while the darker shading represents moisture content above field capacity. A continuous horizontal line marks the permanent 
wilting coefficient for each depth. Precipitation is shown in the bar graphs. At M-2, four replicated gravimetric samples were collected 
each month during 1963; their average moisture content is indicated by dots. 



49 



_c 
<-> 

c 



c 
o 



o 
o 




5 8 



^ 2 



oo 



CM "* 




2$ 

v. 5 



5* 



CM 



CO 

o 

co 


i 





o 
o 




CM 
U 






00 


5 


00 



- c - 

5 ■= o 



co 
O 
O 




16 Graphic comparison of monthly precipitation in 1962 and 1963 at the mesa-top sites and at the canyon-bottom site. 



50 



warmed or replaced rapidly, and the low wind velocities 
present on the canyon floor allow temperatures there 
to build up more. 

The cold air lake that occurs at night increases in depth 
during the winter and influences air temperature 
minima to over 50 feet above the canyon floor. Again, as 
is shown in figure 18, the upper slopes were warmer at 
night than both the mesa top and canyon floor. This is 
a common temperature phenomenon (Geiger, 1957, 
p. 205). 

Soil temperature. Two generally known features of 
soil temperature are illustrated by our data. First, the 
amount of variation is greatest near the surface and 
decreases with increase in depth to about 12 inches, where 
there is little fluctuation throughout the year. Secondly, 
soil temperatures, except near the surface, are more 
moderate than air temperatures, both warmer in winter 
and cooler in summer. Since soil temperatures are con- 
trolled, in part, by the composition of the soil, overall 
comparisons have not been made. 

Precipitation. On the mesa tops, precipitation varies 
directly with increase in altitude, the highest site, at 
Park Point, receiving more precipitation than any other 
(fig. 16). Elevation is less important as a control in the 
canyons. For example, C-2, in the bottom of Navajo 
Canyon, received about the same amount of moisture 
as M-2, 800 feet above. 

The long-term data from the Weather Bureau station 
show that there are generally two wet seasons each year — 
one in late winter and another in late summer, with 
August being the wettest month. Our data show that 
this pattern is characteristic of Mesa Verde as a whole. 

Almost half of the yearly precipitation occurs as snow, 
with the greatest snowfall coming in the month of 
January. Snowstorms are not unusual as late as April, 
particularly at the higher elevations. 

The effect of snow on soil temperature and moisture 
was complicated because of movements of snow by 
changing wind. This circumstance was most pronounced 
at Park Point, where areas covered by a drift 1 week 
were free of snow the next. 

Relative humidity. The humidity record of M-2 may 
be considered typical of most of the mesa top. Humidity 
at the canyon floor and other low areas is markedly 
different, since these localities are subject to cold-air 
drainage. The C-2 data, as well as personal observations, 
indicate that air at the bottom of the canyon is saturated, 
or nearly so, almost every evening of the year. 

Evaporation. Because of consistently poor evaporation 
records, comparison of evaporative rates between sites is 
not possible. However, by selecting five intervals of 6 
days each during which there were continuous atmo- 
graph records (at sites having this instrument), we did 
find that the amount of evaporation appeared to be 
dependent more on wind than on temperature. Evapora- 



90 



Temperature 
in degrees 
Fahrenheit 




17 Graph showing relationship of air temperatures to exposure 
under cloudless skies. As shown, the heat load varies from a 
summer maximum on the east-northeast exposure (G-15) to a 
winter maximum on the west-southwest exposure (C— 1), 



51 




6400 



Canyon 

50^95 bottom L: 




C2 



18 Air-temperature profiles of the west-southwest-facing slope in Navajo Canyon, showing the pronounced cold-air drainage at the 
bottom and the "thermal zone" on the talus. The profile at left shows minimum and maximum temperatures during August 13-19, 196 i. 
while the profile at right gives only minimum temperatures during the winter of 1963—64. 



tion was lowest at C-2, higher at M-2 and M-l, and 
highest at windswept M-3. 

Wind. The prevailing winds at Mesa Verde are south- 
westerly. Spring and early summer are the windiest 
times, with the wind diminishing to its lowest point in 
winter (fig. 19). 

Ml and M-3, near the extremities of the mesa, ex- 
perienced more wind than M-2, the middle mesa-top 
site. This suggests that topographic setting has more 
influence on wind than does altitude. M-l, at the south- 
ern end of the mesa, was influenced by the nearby 
Mancos River canyon, whose northeast-southwest orien- 
tation acts as a natural wind funnel. Since the prevailing 
winds there are generally from the southwest, the spill- 
over from the canyon probably accounted for the small 
increase in wind at this site, in comparison with the 
situation at M-2. 

C-2, on the canyon floor, had the least wind. Usually, 
the wind blew up-canyon during the day, and the cold 
air draining off the mesa tops and slopes produced 
down-canyon breezes at night. 

COMPARISON OF WEATHER BUREAU 
STATION AND M-2 SITE 

The 41 -year record of the park's Weather Bureau 
station provides valuable information on the climate of 
the Mesa Verde. Our M-2 data supplement the Weather 
Bureau record by adding data on hour-to-hour tempera- 
ture conditions and on factors not previously measured 
at that station. In addition, our study provides a means 
of testing how representative the long-term record is for 
the mesa as a whole. 

Although the Weather Bureau station and M-2 were 



within a mile of each other and had similar topographic 
settings, their weather measurements do not agree 
closely. These unexpected results are probably due, in 
part, to the fact that the Weather Bureau station is in a 
small enclosure, which of course is influenced by adja- 
cent buildings and trees. 

Both maximum and minimum air temperatures were 
several degrees lower at M-2 than at the Weather Bureau 
station. This relationship was consistent throughout the 
2 years of measurement. Actually recorded temperatures 
were more alike between the Weather Bureau station and 
M-l lying 5 miles to the south and about 500 feet lower in 
elevation. 

The occasional lack of accord in the precipitation 
records is more understandable. In 1962, M-2 had about 
1.5 inches more precipitation than did the Weather 
Bureau station, but in 1963 it had 0.5 inch less. This 
erratic pattern occurred from month to month as well, 
and can be expected in an area where rainfall is com- 
monly very localized. 

COMPARISON OF MESA-TOP SITES 

The three environment measurement sites on top of 
the mesas gave some indication of how factors vary along 
an elevational gradient. 

Air temperature. M-2 recorded the lowest tempera- 
ture of the mesa-top sites, -26° F., and M-l recorded 
the highest temperature, 98° F. As pointed out earlier, 
the temperature regime at M-3 was surprisingly mod- 
erate, diurnal and seasonal temperatures fluctuating 
much less than at the other sites. In winter servicing 
trips, we often found that Park Point was the warmest 
spot on Mesa Verde. This is to be expected however, 



52 



since temperature variations decrease with increasing 
altitude and wind, and Park Point was the highest and 
windiest site. 

Precipitation. The sample of a given rain or snow- 
storm caught in a gage varies with the amount of wind. 
Since our sites differed in this respect, comparison 
between them is not meaningful. It is clear, however, 
that annual precipitation increased with increasing alti- 
tude, being greatest in 1962, when the stand at the 
lowest mesa elevation received about two-thirds as much 
precipitation as the stand in the middle of the mesa and 
about half as much precipitation as the stand at Park 
Point. These differences resulted largely from variations 
between stations during the January-August interval. In 
1963, the difference between stands was largely due to 



the fact that the stand at the highest elevation received 
almost twice as much precipitation (nearly 8 inches) as 
the other two during August, which was an exceptionally 
wet month. 

Relative humidity. This was lowest at M-l, partic- 
ularly in 1962, when this site received much less rainfall 
than the other mesa-top sites. M-2 and M-3 averaged 
about the same, although the humidity was not nearly 
as variable at higher M-3. Because of rapid, short-term 
fluctuations often associated with local showers, average 
values based on daily maxima and minima are not to be 
considered too significant. 

Evaporation. This was greater at the ends of the mesa 
than in the middle, primarily due to more wind. M-3 
had the highest values in both 1962 and 1963. 



1!) Graph showing average wind velocities at the mesa-top and canyon-bottom sites in 1962 and 1963. Averages for servicing intervals 
and for months arc indicated by light lines and heavy dotted lines, respectively. The gap in the M-3 record, in November 1963, was due 
lo instrumenl failure during the firsl week of that month. 

Wind Velocity 
in miles per hour 




53 



20 



Graph showing progressions of five climatic variables at C-2 and M-2 on June 22, 1963, a cloudless day. 



110 



Soil Temperature 
at 2 inches 




10 12 

Noon 



4 6 8 10 12 



COMPARISON OF MIDDLE MESA-TOP 
AND CANYON- BOTTOM SITES 

Mesas and plateaus are striking features of a landscape, 
but Mesa Verde is especially impressive because of the 
many deep canyons that dissect the upland surface. Such 
contrasting features as fiat mesa tops, cliffs and steep 
slopes, and narrow, sometimes flat canyon floors produce 
a variety of landscape types. Our data clearly show the 
effects of elevation and topographic setting on local 
stands or ecosystems. 

Solar radiation. There are two notable differences in 
the solar radiation regimes between the mesa tops and 
canyons. First, the period of direct illumination is shorter 
in the canyon because the sun's rays are intercepted by 
the cliffs early and late in the day. Secondly, daylight 



begins and ends more abruptly in the canyon. These 
conditions are shown graphically in figure 20, which plots 
the progression and interaction of several factors at M-2 
and C-2. In 1963, incoming radiation at C-2 was almost 
10 percent lower than that at M-2. This was caused 
by the "cliff effect." 

Precipitation. Month-to-month differences in precipi- 
tation between the M-2 and C-2 were slight. 

Wind. At C-2, wind velocity was about half that 
recorded at M-2, on the mesa top above. Nocturnal cold 
air movement may account for some of the wind along 
the floors of the canyons. 

The significant differences in temperature, humidity, 
and evaporation rates between M-2 and C-2 (fig. 20) 
are definitely attributable to cold-air drainage, the 
controlling feature on the canyon floor. 



54 



120 




10 12 

Noon 



COMPARISON OF CANYON SITES 

The canyons contain a variety of ecosystems resulting 
from differences in altitude, soil parent material, sub- 
strate stability, exposure to solar radiation, and tempera- 
ture related to cold-air drainage. 

The three sites in Navajo Canyon were about one-half 
mile due west of park headquarters and 1 % miles south- 
west of the middle mesa-top site, M-2. Navajo Canyon, 
like many others in Mesa Verde, is oriented northwest- 
southeast. Consequently, the slopes receive different 
amounts of solar radiation, which results in the north- 
east-facing (west side) slope being somewhat cooler and 
more moist than the opposite slope. 

Nocturnal conditions play a major role in controlling 
the vegetation at C-2 but have little effect on C-l and 



C-3 nearby. Exposure to incoming solar radiation or to 
insolation appear to be the major cause of differences in 
the stands at C-l and C-3. Therefore, daytime condi- 
tions, especially on a year-round basis, are important at 
the two canyon-slope sites. 

Air- temperature averages at C-l and C-3 show sur- 
prising similarities (table 11). Relative snow cover and 
soil moisture conditions were found to reflect the slope 
differences more vividly. The more direct insolation on 
the southwest-facing slope in winter is felt to be responsible 
for the greater aridity at C-l. 



55 






*& i . 



v «£. 



^i^Pl- 



?~ 



li 




~**JF 



A* 




y : 






y*^> 









5^- 



--' ** 






iiri 















CHAPTER 5 



the environment and the prehistoric occupation 



Information on the soils, climate, and vegetation of Mesa 
Verde contributes to an understanding of the settlement 
pattern and fanning practices of the Pueblo Indians who 
lived here prehistorically. The techniques of many 
disciplines, including floristics, palynology, and dendro- 
climatology, have all been brought to bear on these 
cultural problems. 

EVIDENCE OF PREHISTORIC 
CLIMATE 

Identification of plant remains recovered in the exca- 
vation of certain cliff dwellings on Wetherill Mesa indi- 
cates a flora similar to that of today (Welsh, MS.). In a 
preliminary statement, Schoenwctter (MS.) reported 
that the fossil pollen record gave no indication that a 
major climatic change has occurred since the Indians 
withdrew from the area at the end of the 13th century. 
According to a later report by Martin and Byers (1965, 
p. 122), "The main stratigraphic event in the pollen 
sequence of the last 1,000 years is a relative increase in 
juniper and pine pollen following abandonment 700 
years ago." Although this increase may also reflect a 
minor climatic change, it is probably "the result of 
secondary plant succession with juniper and then pinyon 
invading fields when human disturbance ended" (ibid.). 
Palcoclhnatic studies by Fritts, ct al. (1965) were based 
upon the interpretation of present and past growth 
patterns in pinyon, Utah juniper, and Douglas-fir. 
Tree-ring chronologies for these species indicate that 
intense droughts occurred throughout the time of 
Pueblo occupation and well into the 1 7th century. These 
dry periods have not been surpassed since then. 

In light of these data and studies, it would appear that 
the climate of today approximates that of the 13th 
century in most significant aspects. 



INFLUENCE OF ENVIRONMENT 
ON THE PUEBLOAN CULTURE 

The prehistoric sites of Mesa Verde are not distributed 
uniformly over the plateau but are concentrated in a 
belt along the 7,000 -foot contour, about midway between 
the Mancos River canyon and the escarpment of the 
North Rim (Hayes, 1964). This concentration was 
doubtless the result of many factors, including those of 
vital concern to an agrarian people — water from seeps 
and springs; large areas of deep, fertile soil; and moderate 
climate. The environment of the middle mesa-top site, 
M— 2, may be considered most typical of that in which 
the aborigines spent much of their time. There is no 
direct evidence to prove that the Indians farmed the 
middle mesa top, but archeologists feel strongly that they 
did. This central belt has extensive, deep soils with more 
than adequate nutrients. The lower end of the mesa may 
have been too hot and dry for farming, and the higher 
parts may have lacked adequate soil. 

There is ample evidence of farming in the washes and 
gullies of the mesa rims and on the canyon slopes. As 
the population grew, it is reasonable to assume that some 
marginal areas, places difficult to till, had to be exploited 
in the production of food, primarily maize, beans, and 
squash. Consequently, systems of check dams and farm- 
ing terraces were constructed wherever possible. Accord- 
ing to Rohn (1963, p. 442), each check dam consisted of 
rough-hewn sandstone blocks stacked across a small, 
intermittent stream channel to form a thick wall with a 
marked upstream batter and a level top course. Such a 
system trapped the runoff water, causing fine soil particles 
and organic debris to be deposited behind the stone walls. 
Parts of some hillsides were also terraced, occasionally 
in conjunction with the systems of check dams in the 
erosional channels. These terraces used available moisture 



271-475 0-69— 5 



57 




• farming terrace 

I I top of Mesa 




21. Maj) showing locations V 

of prehistoric farming terraces on 
Wetherill Mesa and in 

adjacent canyons. 



to advantage and undoubtedly increased the annual 
harvests considerably. 



The distribution of farming terraces was studied to 
determine whether the use of those slopes and mesa rims 
that harbor more favorable moisture regimes was 
intentional. The distribution pattern of terraces on 
Wetherill Mesa, mapped during the archeological 
survey (Hayes, 1964), is shown in figure 21. The pattern 
indicates that the more mesic canyon and mesa slopes 
were selected for agricultural purposes. Of the terrace 
systems on talus slopes, about 75 percent of the sites 
surveyed have a northeastern exposure and about 25 
percent of the sites have a southwestern exposure. Even 
more revealing are the "contour" terraces — extensive 
hillside steps not unlike those found today in the Orient 
and in the vineyards of Europe — which are found, with 
few exceptions, on the northeastern exposures of Wetherill 
Mesa. (Discussions in ch. 4 give some information that 
may explain this apparent preference for northeastern 
exposures as locations for farming plots.) 

The combination of favorable temperature conditions, 
as a result of exposure and the stratification of thermal 
zones, slightly higher humidity, and adequate soil 
moisture on the northeastern slopes create what may be 
the most favorable environment for maize agriculture 
in the entire Mesa Verde. 

There is no direct evidence that the canyon floors were 
cultivated. We might conclude that cold-air drainage 
makes this habitat unsuitable for maize and other 
vegetables, but some check dams at the base of talus 
slopes near the canyon floors suggest that farming may 
have been at least marginal in these places. Moreover, 
soil moisture conditions here may have been more favor- 
able than they are today, for Reed's (1958, pp. 615-167) 
investigations in Mancos Canyon suggest that the present- 
day terraces in Mesa Verde were the alluvial floors of 
the canyons in prehistoric times. The arroyo cutting 
which produced the present terraces may have started 
as late as 1880. 

Farming sites along the mesa-top rims are also pre- 
dominantly on northeastern exposures (fig. 21). Sixty- 
percent of those surveyed face approximately northeast, 
while 40 percent have a southwestern exposure. The 
northeast-facing sites receive less insolation, and late- 
lying snow beds improve moisture conditions in the soil. 

In conclusion, it appears that the Pueblo Indian 
farmers deliberately selected the more mesic exposures 
wherever possible. We do not know if the choice was 
made by reasoning that crops would grow best where 
snow persisted longer and temperatures were more 
favorable, or whether it was arrived at by trial-and-error. 
Perhaps trial-and-error was supplemented by increased 
knowledge of the landscape and by observations of crop 
growth throughout the seasons. From what clues we have 
as to their farming practices, it is evident that these 
people were skilled in the management of their most 
priceless natural resources — soil and water. 



58 



references 






Arrhenius, Gustaf, and Enrico Bonatti 
1965. The Mesa Verde Loess. Memoirs of the Society 
for American Archaeology, no. 19; American 
Antiquity, vol. 31, no. 2, pt. 2, pp. 92-100. 
Salt Lake City. 

Benson, Lyman 
1957. Plant Classification. D.C. Heath and Company. 
Boston. 

Bradley, William C. 

1963. Large-scale Exfoliation in Massive Sandstones 
of the Colorado Plateau. Geological Society of 
America, bulletin 74, pp. 519-527. New York. 

Conrad, V., and L. W. Pollack 

1950. Methods in Climatology, Harvard University 
Press. Cambridge. 

Cottam, C, and J. T. Curtis 
1956. The Use of Distance Measures in Phytosocio- 
logical Sampling. Ecology, vol. 37, pp. 451-460. 
Durham. 

Daubenmire, R. F. 

1959. Plants and Environment. John Wiley and Sons, 
New York. 



Erdman, James A. 
MS. Ecology of the Pinyon-Juniper Woodland of 
Wetherill Mesa, Mesa Verde National Park, 
Colo. Unpublished M.A. thesis, 1962. University 
of Colorado. Boulder. 

Fritts, Harold C, David G. Smith, and Marvin A. 
Stokes 
1965. The Biological Model for Paleoclimatic Inter- 
pretation of Mesa Verde Tree-Ring Series. 
Memoirs of the Society for American Archae- 



ology, no. 19; American Antiquity, vol. 31, 
no. 2, pt. 2, pp. 101-121. Salt Lake City. 

Geiger, Rudolf 

1957. The Climate Near the Ground. Harvard 
University Press. Cambridge. 

Gittings, Edwin B. 

1941. Supplementary Climatic Notes for Colorado, 
in Climate and Man, Yearbook of Agriculture, 
pp. 807-808. U.S. Department of Agriculture. 
Washington. 

Glock, Waldo S. 
1937. Principles and Methods of Tree-Ring Analysis. 
Carnegie Institution of Washington, publica- 
tion 486. Washington. 

Hack, John T. 

1942. The Changing Physical Environment of the 
Hopi Indians of Arizona. Papers of the Peabody 
Museum of American Archaeology and Eth- 
nology, Harvard University, vol. 35, no. 1. 
Cambridge. 

Hanson, Herbert C, and Ethan D. Churchill 
1961. The Plant Community. Rheinhold Publishing 
Corporation. New York. 

Hayes, Alden C. 

1964. The Archeological Survey of Wetherill Mesa. 
Archeological Research Series 7-A. National 
Park Service. Washington. 
Hunt, C. B. 

1956. Cenozoic Geology of the Colorado Plateau. 
Geological Survey, professional paper 279. 
Washington. 



59 



Johnsen, Thomas N., Jr. 

1959. Longevity of Stored Juniper Seeds. Ecology, vol. 
40, pp. 487-488. Durham. 

Marr, John W. 
1961 . Ecosystems of the East Slope of the Front Range 
in Colorado. University of Colorado Studies, 
Series in Biology, no. 8. Boulder. 

Martin, Paul S., and William Byers 
1965. Pollen and Archaeology at Wetherill Mesa. 
Memoirs of Society for American Archaeology, 
no. 19; American Antiquity, vol. 31, no. 2, pt. 2, 
pp. 122-135. Salt Lake City. 

Meagher, G. S. 
1943. Reaction of Pinon and Juniper Seedlings to 
Artificial Shade and Supplemental Watering. 
Journal of Forestry, vol. 41, pp. 480-482. 
Washington. 

Nord, Eamor C. 

1959. Bitterbrush Ecology — Some Recent Findings. 
U.S. Forest Service, Pacific Southwest Forest and 
Range Experiment Station Research, note 148. 
Berkeley. 

Oosting, Henry J. 
1956. The Study of Plant Communities. W. H. 
Freeman. San Francisco. 

Reed, Erik K. 

1958. Excavations in Mancos Canyon, Colorado. Uni- 
versity of Utah Anthropological Papers, no. 35. 
Salt Lake City. 

Roberts, Ray C. 

MS. Initial Field Review of the Soils on Wetherill 
Mesa, Mesa Verde National Park, Colorado. 
Unpublished manuscript, 1960, on file at Mesa 
Verde National Park, Colo. 



Rohn, Arthur H. 

1963. Prehistoric Soil and Water Conservation on 
Chapin Mesa, Southwestern Colorado. Ameri- 
can Antiquity, vol. 28, no. 4, pp. 441^55. Salt 
Lake City. 

SCHOENWETTER, JAMES 

MS. Pollen Stratigraphy of the Wetherill Mesa Re- 
gion. Unpublished manuscript, 1960, on file at 
Mesa Verde National Park, Colo. 

Trewartha, Glenn T. 

1954. An Introduction to Climate. McGraw-Hill. New 
York. 

Wanek, Alexander A. 

1959. Geology and Fuel Resources of the Mesa Verde 
Area, Montezuma and La Plata Counties, Colo- 
rado. Geological Survey, bulletin 1072-M. 
Washington. 

Watson, Don 
1934. Unusual Weather. Mesa Verde Notes, vol. 5, 
no. 1, pp. 16-17. Mesa Verde National Park, 
Colo. 

Welsh, Stanley L. 

MS. Identification of Vegetal Materials, Report no. 
7. Unpublished manuscript, 1961, on file at 
Mesa Verde National Park, Colo. 

Welsh, Stanley L., and James A. Erdman 
1 964. Annotated Checklist of the Plants of Mesa Verde, 
Colorado. Brigham Young University Science 
Bulletin, Biological Series, vol. 4, no. 2. Provo. 

White, Everett M. 

MS. Wetherill Mesa Soil Investigation. Unpublished 
manuscript, 1960, on file at Mesa Verde Na- 
tional Park, Colo. 



60 






appendix 



ANNUAL SUMMARIES OF ENVIRONMENT DATA 

Station: M-l; elevation: 6,650 feet; site: Mesa top; year: 1962 





Air temperature, degrees 


F. 


Percent relative humidity 


Solar radiation, 


Wind 


Month 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


G-cal./sq. cm. 


Total 
miles 


Veloc- 
ity, 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Total 


Mean 


m.p.h. 




46 
58 
65 
80 
83 
95 
97 
98 
90 
76 
67 
57 


—2 

—3 

5 

26 

24 

41 

46 

40 

36 

36 

16 




37 
43 
45 
67 
71 
84 
89 
89 
77 
67 
55 
44 


13 
23 
22 
36 
40 
49 
56 
54 
49 
41 
32 
22 


25.3 
33. 1 
33. 7 
51.5 
55.7 
66.7 
72.9 
71.6 
63.5 
53.6 
43.4 
32.9 


100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 


20 
15 
8 
2 
1 
2 
2 
2 
8 
2 
4 
16 


93 
94 
73 
56 
46 
36 
51 
44 
65 
70 
69 
91 


33 
34 
23 
12 
9 
8 
11 
12 
23 
19 
26 
36 


63.2 
63.9 
47.9 
34. 1 
27.3 
22.4 
31. 1 
27.9 
44. 1 
44.4 
47.7 
63.4 






4,224 
3,345 
4,594 
5,006 
5,254 
4,915 
4,544 
4,810 
4,319 
4,272 
3,831 
3,674 


5. 7 








5.0 


March 






6.2 


April 






7.0 








7.0 








6.8 


Tulv . 






6. 1 








6.4 








6.0 


October . . .... 






5. 7 


November 






5.4 


December 






4.9 










Year 


98 


—3 


64 


36 


50.0 


100 


1 


66 


21 


43. 1 






52, 788 


6.0 













Precipi- 
tation 

in 
inches 
water 


Soil temperature, degrees Fahrenheit 


Month 


2-inch depth 


6-inch depth 


12-inch depth 




Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 




January 

February 

March 


0.25 

.35 

.80 

.47 

.20 

.09 

.30 

.28 

1.95 

2.38 

1.30 

.80 




























































































April 

May 

June 

July 


88 
97 
116 
117 
120 
110 
83 


37 
36 
52 
62 
59 
41 
41 


78 

86 

104 

110 

110 

94 

75 


47 
51 
62 
69 
67 
58 
46 


62.5 
68.4 
83. 1 
89.5 
88.9 
75.8 
60.3 


69 
75 
88 
90 
92 
85 
71 


48 
47 
59 
72 
71 
50 
49 


64 
69 
81 
86 
87 
77 
64 


53 
58 
69 
76 
76 
66 
53 


58.4 
63.3 
74.6 
81.2 
81.5 
71.6 
58.4 


62 
68 
80 
82 
84 
78 
65 


52 
50 
60 
74 
73 
56 
55 


59 
63 
73 
80 
81 
73 
61 


55 
59 
69 
76 
77 
69 
58 


56.5 
61. 1 
71. 1 
78.3 


August 


78.9 


September 


71. 1 


October 


59.4 


December 


32 


22 


29 


25 


26.9 


32 


26 


30 


27 


28.4 


34 


27 


32 


29 


30.2 






Year 


9. 17 

































































Note. —Italic figures represent a sample size of less than 28 days. 



61 



APPENDIX— ANNUAL SUMMARIES— Continued 

Station: M-l; elevation: 6,650 feet; site: Mesa top; year: 1963 





Ai 


r temperature, degrees 


F. 


Percent relative humidity 


Solar radiation, 


Wind 


Month 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


G-cal./sq. cm. 


Total 
miles 


Veloc- 
ity. 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Total 


Mean 


m.p.h. 


January 

February 

March 


44 
61 
66 
76 
84 
95 
97 
92 
86 
84 
64 
52 


-23 

2 

8 

16 

29 

36 

52 

52 

46 

30 

16 

2 


34 
46 
50 
59 
77 
83 
91 
83 
81 
71 
53 
41 


// 
24 
25 
29 
44 
48 
59 
57 
52 
43 
29 
17 


22.3 
35.3 
37.8 
44.2 
60.5 
65.3 
75.0 
69.8 
66.4 
57.0 
40.9 
28.8 


100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 


/; 

12 

7 

4 

6 

7 

8 

13 

11 

12 

16 

12 


90 
88 
79 
69 
46 
53 
60 
91 
73 
63 
89 
86 


47 
35 
21 
20 
12 
17 
18 
26 
20 
26 
30 
36 


68.5 
61.5 
49.6 
44. 7 
29. 1 
35. 1 
38.8 
58.7 
46.8 
44.5 
59. 5 
60.9 






3,277 
3,636 
4,926 
5,268 
4,826 
4,945 
4,372 
3,806 
4,009 
4,072 
4,836 
3,668 


4 4 






5 5 






6. 6 


April 






7 3 


M ay 






6 5 


June 






6. 9 


Tuly 






5. 9 


August 

September 






5. 1 






5. 5 


October . . 






5. 5 








6. 7 


December 






4. 9 










Year 


97 


-23 


64 


37 


50.3 


100 


4 


74 


26 


49.8 






51,641 


5. 9 













Precipi- 
tation 

in 
inches 
water 


Soil temperature, degrees Fahrenheit 


Month 


2-inch depth 


6-i 


nch depth 




12-inch depth 




Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 






1.50 

1.20 

.85 

.48 

.06 

.02 

2.25 

3.96 

.72 

1.55 

.79 

.50 


34 

51 

70 

78 

98 

115 

115 

112 

101 

91 

57 

32 


22 
29 
30 
34 
51 
55 
66 
61 
55 
37 
28 
19 


31 
38 
51 
67 
88 
101 
107 
99 
93 
76 
48 
28 


28 
33 
36 
45 
60 
65 
75 
69 
62 
49 
33 
24 


29. 1 
35. 1 
43.4 
55.6 
73.9 
83. 1 
90.6 
84.0 
77.3 
62.4 
40. 5 
25.9 


33 
40 
57 
64 
80 
92 
96 
94 
85 
75 
48 
32 


25 
29 
31 
40 
55 
64 
71 
66 
62 
44 
30 
23 


31 
35 
43 
57 
74 
82 
91 
86 
79 
64 
42 
28 


28 
32 
37 
49 
64 
71 
80 
75 
67 
55 
37 
25 


29.6 
33.6 
40. 1 
52.9 
68.9 
76.4 
85.4 
80.3 
73.3 
59. 1 
39. 6 
26.5 


35 
39 
52 
59 
70 
78 
84 
83 
74 
68 
45 
33 


26 
30 
33 
43 
56 
61 
70 
65 
62 
46 
30 
23 


33 
36 
42 
54 
66 
72 
80 
77 
70 
59 
41 
28 


30 
33 
39 
50 
62 
67 
76 
73 
66 
56 
38 
25 


31. 1 


February 

March 


34.9 
40.2 


April 

May 


52.2 
63.9 


June 

Tuly 


69.3 
78. 1 


August 

September 

October 

November 

December 


74.9 
68.4 
57.4 
39.4 
26.6 






Year 


13.88 


115 


19 


69 


48 


58.4 


96 


23 


59 


52 


55.5 


84 


23 


55 


51 


53.0 



Note.— Italic figures represent a sample size of less than 28 days. 



62 



APPENDIX —ANNUAL SUMMARIES— Continued 

Station: M-2; elevation: 7,150 feet; site: Mesa top; year: 1962 





Air temperature, degrees 


F. 


Percent relative 


numidity 


Solar radiation, 


Wi 


nd 


Month 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


G.-cal./sq.cm. 


Total 
miles 


Veloc- 
ity 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Total 


Mean 


m.p.h. 




52 
56 
63 
78 
78 
91 
91 
94 
86 
74 
63 
53 


-11 

-10 

2 

24 

23 

38 

48 

46 

38 

34 

13 

-2 


38 
42 
45 
64 
68 
80 
84 
86 
75 
64 
52 
44 


13 
21 
21 
34 
38 
47 
54 
55 
49 
39 
30 
20 


25.6 
31.3 
32.6 
49.2 
52.8 
63.9 
69. 1 
70.2 
61.7 
51.5 
41. 1 
31. 7 


100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 


20 
22 
16 
12 
5 
10 
10 
10 
17 
15 
10 
18 


94 
92 
81 
70 
62 
54 
68 
59 
77 
91 
86 
89 


35 
37 
28 
22 
20 
18 
19 
21 
32 
34 
36 
34 


64.8 
64.3 
54.8 
46. 1 
40. 7 
36.0 
43.8 
40.0 
54.9 
62.8 
60.9 
61. 7 






3,994 

3, 129 
4,317 
4,331 

4, 155 
3,947 
/, 822 
3,652 
3,692 
3,431 
3,331 
3,049 


5.4 








4. 7 








5.8 


April 






6.0 


May 


20, 874 
22, 100 
20, 320 
19,950 
14,423 
11,542 
7,022 
6,502 


673 
737 
655 
644 
481 
372 
234 
210 


5.6 




5.5 


Tuly 


4. 2 


August 

September 

October 


4.9 
5. 1 
4.6 


November 


4.6 


December 


4. 1 






Year 


94 


-11 


62 


35 


48.5 


100 


5 


77 


28 


52.5 






42, 850 


5.0 













Precipi- 
tation 

in 
inches 
water 


Soil temperature, degrees Fahrenheit 


Month 


2-inch depth 


6-inch depth 




12- 


inch depth 






Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 




January 

February 

March 


.75 

2.70 

1.30 

.65 

.87 

.20 

1.03 

.23 

2.33 

2.74 

1.70 

1.30 




























































































April 

May 

June 


84 

93 

111 

113 

114 

107 

82 

64 

42 


32 
33 
47 
60 
56 
42 
34 
25 
24 


75 

83 

100 

104 

106 

90 

70 

48 

34 


42 
46 
59 
65 
65 
55 
39 
30 
27 


58.9 
64. 2 
79.6 
84.9 
85.6 
72.4 
54.4 
39.0 
30. 1 


68 
76 
86 
87 
86 
77 
59 
45 
34 


42 
43 
53 
65 
61 
41 
33 
20 
17 


63 
67 
80 
82 
81 
68 
50 
34 
29 


49 
53 
65 
69 
67 
55 
38 
26 
25 


55. 8 
60. 1 
72. 5 
75.5 
74.4 
61.8 
44. 1 
29.8 
26.8 


61 
68 
81 
82 
84 
77 
62 
50 
35 


49 
49 
58 
72 
72 
54 
45 
30 
23 


58 
62 
74 
80 
80 
71 
55 
41 
31 


53 
57 
69 
75 
76 
67 
50 
38 
28 


55. 1 
59. 8 
71.8 


Tuly 


77. 3 


August 

September 

October 

November 


78.0 
68.7 
52.6 
39. 5 


December 


29.6 




15.80 

































































Note.— Italic figures represent a sample size of less than 28 days. 



63 



APPENDIX —ANNUAL SUMMARIES— Continued 

Station: M-2; elevation: 7,150 feet; site: Mesa top; year: 1963 





Air temperature, degrees 


F. 


Percent relative humidity 






Wind 
















Solar radiation, 
G-cal./sq. cm. 


























Month 


Extreme 


Mean 




Extreme 


Mean 










Veloc- 










Mean 






Mean 






Total 
miles 


ity. 
























m.p.h. 




Max. 


Min. 


Max. 


Min. 




Max. 


Min. 


Max. 


Min. 




Total 


Mean 








44 


-26 


32 


8 


20.3 


100 


21 


93 


43 


67.9 


5,494 


177 


3, 156 


4.2 


February 


58 


2 


45 


23 


33.6 


100 


18 


90 


38 


64. 1 


8, 165 


292 


3, 397 


5. 1 


March 


63 


12 


47 


24 


35.4 


100 


15 


84 


29 


56.7 


13,264 


428 


4,516 


6. 1 


April 


70 


15 


55 


28 


41. 5 


100 


8 


73 


25 


48.9 


16,489 


550 


4,687 


6.5 


May 


77 


31 


72 


41 


56.2 


92 


8 


51 


15 


33.0 


20, 992 


677 


4,335 


5.9 


June 


90 


35 


79 


45 


62.0 


96 


9 


55 


19 


36.9 


20,311 


677 


4,394 


6. 1 


Tuly 


93 
88 


50 
50 


86 
79 


56 
54 


71. 1 
66.6 


98 
91 


10 
12 


63 
83 


19 

27 


41.2 
54.9 


20, 286 
15,943 


654 
514 


4,073 
3,476 


5. 5 


August 


4. 7 


September 


83 


44 


78 


49 


63.6 


100 


14 


76 


24 


50.0 


15,649 


522 


3,441 


4.8 


October 


82 


29 


68 


41 


54.5 


100 


16 


72 


31 


51.6 


11,080 


357 


3,406 


4.6 




62 


17 


52 


28 


39.9 


100 


20 


91 


34 


62.4 


7,266 


242 


4,092 


5.6 


December 


51 


4 


41 


17 


29. 1 


100 


18 


86 


34 


60.2 


6,754 


218 


3,017 


4. 1 


Year 


93 


-26 


61 


34 


47.8 


100 


8 


76 


28 


52.3 


161,693 


442 


45, 990 


5.3 





Precipi- 
tation 
in 

. inches 
water 










Soil temperature, degrees Far 


irenheit 










Month 


2-inch depth 


6-i 


nch depth 




12-inch depth 




Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. Min. 




January 

February 


1.60 

1.35 

.95 

.54 

. 12 

.07 

2. 13 

4.54 

.59 

1.77 

.88 

.50 


32 

51 

75 

82 

107 

120 

120 

118 

97 

96 

61 

36 


22 
27 
25 
30 
45 
48 
58 
58 
52 
36 
24 
17 


29 
36 
52 
69 
96 
107 
107 
96 
92 
77 
48 
33 


26 
29 
32 
39 
55 
61 
69 
64 
58 
48 
31 
26 


27.6 
32. 7 
41.7 
53.9 
75.6 
84.0 
87.8 
80.0 
74.9 
62. 7 
39.8 
29.5 


32 
40 
59 
64 
81 
91 
92 
90 
77 
72 
46 
33 


25 
28 
29 
35 
50 
57 
63 
58 
54 
38 
23 
16 


30 
34 
43 
57 
74 
82 
86 
78 
72 
60 
37 
29 


27 
30 
34 
44 
60 
67 
71 
66 
59 
49 
30 
25 


28. 7 
31.8 
38.2 
50.2 
67.0 
74.2 
78. 7 
71.9 
65.8 
54.2 
33.6 
27.4 


35 
37 
52 
59 
75 
85 
87 
87 
75 
68 
46 
36 


23 
29 
31 
40 
54 
65 
71 
67 
61 
45 
29 
24 


33 
35 
40 
53 
69 
77 
83 
78 
71 
58 
39 
32 


28 
31 
37 
48 
64 
72 
78 
74 
66 
54 
36 
28 


30.4 
33.0 


March 


38.4 


April 


50.5 


May 


66.5 


June 


74. 5 


Tuly 


80.5 


August 

September 


76.0 
68.4 


October 

November 

December 


56.4 
37.6 
30. 1 


Year 


15.04 


120 


17 


70 


45 


57.5 


92 


16 


57 


47 


51.8 


87 


23 


56 


51 


53.5 



Note.— Italic figures represent a sample size of less than 28 days. 



64 



APPENDIX— ANNUAL SUMMARIES— Continued 

Station: M-3; elevation: S.575 feet; site: Mesa top; year: 1962 





Air temperature, degrees 


F. 


Percent relative humidity 


Solar radiation, 


Wind 


Month 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


G-cal./sq. cm. 


Total 
miles 


Veloc- 
ity. 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Total 


Mean 


m.p.h. 




50 
50 
55 
68 
70 
81 
84 
88 
79 
66 
58 
48 


-5 
1 

4 
18 
27 
35 
47 
47 
37 
33 
12 



31 
34 
34 
54 
59 
70 
77 
78 
68 
57 
44 
36 


16 
22 
19 
35 
40 
49 
55 
55 
49 
41 
31 
23 


23.6 
28.3 
26.5 
44. 7 
49.5 
59.5 
65.6 
66.5 
58.0 
48.9 
37.7 
29.8 


100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 


23 
21 
17 
12 
9 
14 
17 
12 
16 
14 
18 
20 


85 
86 

70 
64 
54 
47 
67 
55 
74 
71 
71 
74 


38 
50 
34 
25 
24 
22 
26 
23 
34 
33 
45 
42 


61.5 
67.9 
51.8 
44.5 
39.0 
34. 7 
46.6 
39. 2 
53.6 
52.3 
58.0 
58.6 






9, 148 
7,826 
8,810 
7,916 
8,304 
7,427 
7, 167 
4,835 
6,506 
6,376 
6,802 
6, 134 


12 3 








11. 6 








11. 8 








11. 








11. 1 








10. 2 


Tulv 






9. 6 


August 






10 1 






9.0 








8. 6 








9. 5 








8.2 










Year . . 


88 


-5 


54 


36 


44.9 


100 


9 


68 


33 


50.6 






87, 251 


10. 3 













Precipi- 
tation 

in 
inches 
water 


Soil temperature, degrees Fahrenheit 


Month 




2-i 


nch depth 




6-inch depth 




12- 


inch depth 






Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 




January 

February 


0.75 

2.80 

1.50 

.39 

.93 

1.03 

2.02 

1.97 

2. 13 

2.94 

1.50 

.90 






























































March 
































April 

May 

June 

Tulv 


72 

79 

103 

104 

105 

96 

76 

64 

41 


29 
33 
42 
55 
52 
38 
34 
30 
24 


63 
68 
87 
95 
95 
80 
64 
48 
32 


40 
44 
56 
62 
61 
53 
39 
33 
28 


51. 3 
55. 7 
71.6 
78. 7 
77.9 
66.3 
51.7 
40.3 
29.8 


59 
67 
81 
83 
85 
77 
64 
54 
35 


36 
39 
47 
63 
60 
45 
38 
31 
26 


53 
58 
72 
78 
79 
68 
56 
43 
31 


45 
48 
61 
68 
67 
59 
44 
37 
29 


48. 9 
53.0 
66.4 
72.9 
73.2 
63.4 
50.2 
39. 9 
30.4 


54 
59 
72 
74 
76 
69 
56 
48 
33 


39 
40 
49 
64 
63 
48 
41 
32 
26 


49 
53 
64 
71 
72 
63 
51 
41 
31 


45 
49 
61 
68 
69 
60 
47 
38 
29 


47.0 
50.9 
62.7 
69. 7 


August 

September 

October 


70.2 
61.8 
48.8 


November 


39. 4 


December 


30.2 






Year 


18.86 

































































Note.— Italic figures represent a sample size of less than 28 days. 



65 



APPENDIX— ANNUAL SUMMARIES— Continued 

Station: M-3; elevation: 8,575 feet; site: Mesa top; year: 1963 





Air temperature, degrees 


F. 


Percent relative humidity 


Solar rac 


iation, 


Wind 


Month 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


G-cal./sq. cm. 


Total 
miles 


Veloc- 
ity 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Total 


Mean 


m.p.h. 




44 
46 
54 
66 
72 
82 
86 
82 
75 
74 
57 
46 


-20 
20 
5 
13 
32 
38 
50 
45 
44 
29 
20 

/; 


30 
39 
38 
49 
66 
70 
79 
71 
69 
61 
45 
37 


15 
28 
21 
28 
46 
49 
58 
52 
51 
45 
31 
23 


22.5 
33. 5 
29.6 
38.5 
55. 7 
59.8 
68.3 
61.7 
60.4 
52.6 
38.2 
29. 8 


100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 
100 


23 
34 
19 
15 
16 
16 
16 
24 
17 
20 
13 
20 


82 
82 
77 
69 
48 
55 
63 
92 
71 
63 
79 
75 


50 
51 
33 
30 
25 
27 
28 
41 
33 
37 
38 
38 


65. 7 

66. 4 
55.0. 






7,372 
6,208 
7,271 
7,722 
7,326 
7,341 
5,981 
5,919 
5, 752 

3, 814 

4, 468 
6,678 


9 9 


February 






9 2 






9 8 


April 

May 


49.9 
36.3 
40.9 
45.4 
66.2 
51.6 
50.2 
58.6 
56. 6 






10 7 






9 9 






10. 2 


luly 






8. 1 


August 

September 






7 9 






8.0 






7. 5 








8. 5 








8. 9 










Year 


86 


-20 


55 


37 


45.9 


100 


13 


71 


36 


53.6 






75, 852 


9. 1 













Precipi- 
tation 

in 
inches 
water 


Soil temperature, degrees Fahrenheit 


Month 


2-inch depth 


6-inch depth 




12- 


inch depth 






Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 




lanuarv 


1.30 

1.20 

1.00 

.55 

. 16 

.07 

1.97 

7.62 

.45 

2.70 

1.04 

.75 


31 

34 

64 

73 

95 

111 

110 

110 

99 

100 

66 

44 


23 
26 
24 
28 
42 
45 
55 
54 
49 
36 
24 
24 


28 
31 
38 
59 
83 
96 
99 
90 
90 
82 
47 
40 


27 
30 
29 
35 
52 
58 
64 
59 
55 
47 
31 
27 


27. 5 
30.4 
33.2 
47. 1 
67.5 
76.8 
81.8 
74. 5 
72.9 
64.5 
39. 2 
33. 6 


32 
35 
51 
59 
76 
89 
90 
87 
79 
77 
54 
36 


25 
28 
27 
32 
46 
55 
61 
58 
56 
43 
32 
29 


30 
32 
34 
50 
69 
77 
83 
77 
74 
65 
42 
34 


28 
31 
31 
40 
57 
65 
70 
65 
61 
54 
36 
31 


29. 1 

31.4 
32.6 
45.2 
63. 1 
71.2 
76.7 
70. 7 
67.8 
59.9 
38. 8 
32. 7 


34 
35 
45 
53 
68 
79 
81 
80 
71 
70 
49 
36 


25 
28 
28 
35 
48 
59 
66 
63 
61 
49 
34 
32 


31 
33 
34 
46 
62 
71 
77 
72 
69 
61 
42 
35 


29 
31 
32 
42 
59 
67 
73 
68 
65 
58 
39 
34 


29. 9 


February 


32. 1 


March 


33.0 




44. 1 




60.6 




69. 1 


July 


75.3 


August 


70.3 


September 

October 


66.6 
59.8 


November 


40. 5 


December 


34. 6 






Year 


18.81 


111 


23 


65 


43 


54. 1 


90 


25 


56 


47 


51.6 


81 


25 


53 


50 


51.3 







Note.— Italic figures represent a sample size of less than 28 days. 



66 



APPENDIX —ANNUAL SUMMARIES— Continued 

Station: C-l; elevation: 6,500 feet; site: Canyon slope, southwest-facing; year: 1962 





Air temperature, degrees 


F. 


Percent relative humidity 


Solar radiation, 


Wind 


Month 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


G-cal./sq. cm. 


Total 
miles 


Veloc- 
ity 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Total 


Mean 


m.p.h. 


January 


48 
58 
70 
80 
84 
92 
95 
97 
90 
78 
68 
58 


-2 

-2 

5 

27 

27 

53 

51 

46 

38 

35 

17 

3 


39 
44 
47 
67 
71 
88 
89 
89 
78 
68 
56 
46 


16 
23 
22 
36 
40 
55 
55 
55 
49 
40 
31 
22 


27.6 
33.4 
34.4 
51.5 
55.5 
71. 4 
72.0 
72.0 
63.7 
53.7 
43.6 
33.8 


94 

90 

92 

93 

93 

100 

100 

100 

100 

100 

100 

96 


24 
22 
12 
10 

4 
22 
10 

8 
14 
14 
20 
21 


84 
84 
75 
64 
57 
86 
68 
59 
72 
88 
85 
85 


36 
37 
26 
19 
17 
29 
21 
20 
32 
32 
32 
37 


59.9 
60. 7 
50.5 
41.4 
36.9 
57. 3 
44.9 
39.8 
51.9 
60.0 
61.6 
61.2 


















March 










April . . 










May 




















luly 


















































December .... 




















Year . . 


97 


-2 


65 


37 


51. 1 


100 


4 


76 


29 


52.2 























Precipi- 
tation 

in 
inches 
water 


Soil temperature, degrees Fahrenheit 


Month 


2-inch depth 


6-inch depth 


12-inch depth 




Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 




January 


































February 


































March 


































April 




77 
82 
92 
94 
98 
100 
84 
72 


43 
43 
52 
66 
64 
48 
42 
38 


69 
71 
84 
89 
92 
85 
73 
65 


50 
53 
63 
70 
71 
63 
48 
43 


59. 4 
62. 
73. 1 
79.4 
81.6 
74.3 
60.9 
53. 9 


63 
69 
79 
82 
83 
79 
69 
59 


49 
48 
56 
69 
71 
55 
49 
46 


59 
62 
72 
78 
80 
74 
62 
55 


53 
56 
65 
72 
74 
68 
55 
49 


56". 2 
59. 2 
68. 7 
75. 1 
77. 1 
70.9 
58.4 
52. 


59 
64 
75 
77 
81 
77 
66 
53 


50 
49 
56 
69 
71 
60 
53 
49 


56 
59 
69 
76 
78 
73 
61 
53 


53 
56 
64 
72 
74 
70 
58 
49 


54. 5 


May 




57. 6 


June 




66. 5 


July 




73. 7 


August 




76.0 


September 




71. 1 


October 




59.4 


November 




50. 9 


December 








































Year 





































































Note.— Italic figures represent a sample size of less than 28 days. 



67 



APPENDIX— ANNUAL SUMMARIES— Continued 

Station: C-l; elevation: 6,500 feet; site: Canyon slope, southwest-facing; year: 1963 





Air temperature, degrees 


F. 


Percent relative humidity 


Solar radiation, 


Wind 


Month 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


G-cal./sq. cm. 


Total 
miles 


Veloc- 
ity 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Total 


Mean 


m.p.h. 


January 

February 


48 
65 
68 
74 
84 
95 
98 
92 
89 
85 
67 
54 


-20 

3 

13 
17 
32 
37 
54 
52 
47 
32 
18 

5 


34 
48 
52 
59 
77 
82 
92 
84 
83 
72 
55 
43 


10 
24 
25 
30 
43 
48 
59 
56 
52 
44 
30 
18 


21.8 
36.4 
38.4 
44.5 
60. 1 
65.3 
75.0 
69.8 
67.3 
57.6 
42.3 
30.3 


100 

100 

100 

100 

81 

84 

84 

82 

100 

100 

100 

100 


22 

18 

14 

10 

4 

6 

8 

10 

14 

17 

22 

20 


89 
90 
84 
62 
45 
45 
56 
74 
74 
69 
86 
83 


45 
38 
28 
21 
12 
15 
16 
23 
24 
31 
34 
37 


66.9 
63.9 
55.8 
41.2 
28.7 
29.8 
36.5 
48.5 
49.0 
49.8 
60.2 
60.0 


















March 










April 










May 










June 










July 










August 










September 

October 


















November . . 






























Year 


98 


-20 


65 


37 


50.7 


100 


4 


71 


27 


49.2 























Precipi- 
tation 

in 
inches 
water 


Soil temperature, degrees Fahrenheit 


Month 


2-inch depth 


6-inch depth 


12-inch depth 




Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 




January 




33 
59 
65 
68 
80 
92 
97 
96 
93 
92 
68 
52 


25 
29 
31 
37 
49 
55 
61 
61 
57 
46 
32 
25 


31 
46 
51 
59 
75 
82 
89 
88 
89 
78 
57 
38 


28 
33 
37 
44 
58 
64 
69 
67 
64 
55 
39 
30 


29.5 
39.3 
43.9 
51.8 
66.4 
72.7 
78.9 
77. 1 
76.2 
66.5 
48.0 
33.8 


33 
43 
52 
56 
70 
78 
83 
82 
78 
75 
56 
44 


26 
31 
33 
41 
50 
59 
66 
65 
62 
52 
38 
30 


32 
38 
43 
51 
65 
71 
79 
76 
75 
66 
50 
37 


29 
34 
38 
46 
59 
65 
72 
70 
67 
60 
45 
34 


30.3 
36.3 
40.6 
48.9 
61.8 
68.0 
75.5 
73. 1 
71. 1 
63.3 
47.2 
35.2 


35 
42 
49 
53 
67 
75 
80 
80 
75 
73 
56 
45 


25 
31 
34 
41 
49 
60 
67 
67 
65 
55 
41 
32 


33 
38 
41 
49 
62 
69 
76 
75 
73 
66 
51 
39 


29 
35 
38 
46 
58 
64 
72 
71 
69 
62 
47 
36 


30. 9 


February 




36. 1 


March 




39.7 


April 




47.6 


May 




60.0 


June 




66.6 


July 




74. 1 






73. 1 






70.7 


October 




64. 1 


November 




49.0 


December 




37.3 








Year 




97 


25 


65 


49 


57.0 


83 


26 


57 


52 


54.3 


80 


25 


56 


52 


54. 1 









Note.— Italic figures represent a sample size of less than 28 days. 



68 



APPENDIX— ANNUAL SUMMARIES— Continued 

Station: C-2; elevation: 6,382 feet; site: Canyon bottom; year: 1962 





Air temperature, degrees 


F. 


Percent relative 


"mmidity 


Solar radiation, 
G-cal./sq. cm. 


Wind 


Month 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


Total 
miles 


Veloc- 
ity 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Total 


Mean 


m.p.h. 




47 
57 
67 
79 
82 
95 
97 
98 
90 
78 
67 
58 


-7 

-8 

-2 

20 

19 

33 

42 

36 

28 

28 

13 

-6 


38 
44 
46 
66 
71 
83 
90 
90 
79 
68 
55 
44 


8 
19 
17 
29 
34 
42 
50 
48 
43 
34 
25 
14 


23. 1 

31.2 
31.7 
47.4 
52.5 
62.5 
69.8 
68. 7 
61.0 
50.8 
40.2 
29.2 


100 

96 

100 

100 

100 

96 

98 

100 

100 

100 

100 

100 


24 

18 

11 

8 

4 

11 

8 

5 

12 

14 

18 

25 


94 
91 
93 
88 
78 
74 
76 
68 
78 

100 
98 

100 


36 
37 
26 
20 
18 
18 
17 
16 
29 
32 
38 
42 


65.0 
64. 1 
59.5 
53.9 
48.2 
45.6 
46.2 
42.2 
53.6 
66.0 
68.0 
70.7 






1,283 
953 
1,586 
1,907 
2,313 
2,253 
2,079 
2, 159 
1,615 
1,370 
1,049 
954 


1. 7 








1.4 








2. 1 








2.6 


May 


19,631 
21,605 
18, 782 
18, 152 
13,364 
10,559 
7,594 
5,351 


654 
720 
606 
586 
445 
341 
253 
173 


3. 1 




3. 1 


Tulv 


2.8 




2.9 


September 


2.2 


October 


1.8 


November 


1.5 




1.3 








98 


-8 


65 


30 


47.4 


100 


4 


87 


27 


56.9 






19,521 


2.2 













Precipi- 
tation 

in 
inches 
water 


Soil temperature, degrees Fahrenheit 


Month 


2-inch depth 


6-inch depth 


12-inch depth 




Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 




January 

February 

March 


0.65 

2.50 

1. 15 

.65 

.96 

. 18 

.32 

.33 

1.97 

2.52 

1.60 

1. 10 




























































































April 

May 

June 

Tuly 


72 

81 

103 

105 

108 

97 

76 

56 

40 


38 
36 
50 
62 
55 
44 
34 
28 
18 


66 
74 
90 
99 
99 
84 
64 
44 
31 


44 
49 
61 
68 
67 
58 
41 
31 
25 


55.0 
61.3 
75.3 
83.5 
83. 1 
71. 1 
52.4 
37.8 
28.0 


64 
72 
88 
89 
92 
83 
69 
51 
39 


43 
41 
53 
68 
65 
48 
38 
30 
20 


60 
66 
80 
85 
86 
76 
58 
41 
32 


47 
53 
67 
73 
73 
63 
44 
34 
27 


53. 6 
59.4 
72.3 
79.3 
79.6 
69.2 
51.3 
37.5 
29.3 


57 
63 
77 
79 
82 
74 
60 
48 
37 


45 
44 
55 
69 
68 
54 
42 
32 
23 


54 
59 
70 
77 
78 
70 
53 
41 
33 


48 
53 
64 
72 
72 
65 
48 
36 
28 


51. 
56. 1 
67.3 
74.8 


August 

September 

October 

November 

December 


75.2 
67. 1 
50.7 
38.5 

30. 7 


Year 


13.93 

































































Note.— Italic figures represent a sample size of less than 28 days. 



69 



APPENDIX —ANNUAL SUMMARIES— Continued 

Station: C-2; elevation: 0,382 feet; site: Canyon bottom; year: 1963 



Month 



Air temperature, degrees 


F. 


Percent relative humidity 






Wind 














Solar radiation, 
G-cal./sq. cm. 
























Extreme 


Mean 




Extreme 


Mean 










Veloc- 








Mean 






Mean 






Total 

miles 


ity 






















m.p.h. 


Max. 


Min. 


Max. 


Min. 




Max. 


Min. 


Max. 


Min. 




Total 


Mean 






48 


— 28 


34 


4 


18.9 


100 


21 


99 


48 


73.6 


5,393 


174 


1,284 


1. 7 


65 


— 3 


49 


20 


34.2 


100 


16 


100 


39 


69.3 


6,888 


246 


1,006 


1.5 


68 


6 


51 


21 


36. 1 


100 


14 


99 


29 


64. 1 


11, 794 


380 


1,606 


2.2 


75 


13 


60 


25 


42.3 


100 


11 


85 


22 


53.7 


14, 725 


491 


2, 145 


3.0 


84 


25 


77 


37 


56.7 


98 


8 


75 


16 


45.9 


19,824 


639 


2, 194 


3.0 


94 


32 


82 


41 


61.5 


98 


10 


71 


18 


44.8 


19,228 


641 


2,447 


3.4 


97 


44 


91 


52 


71. 7 


99 


10 


80 


19 


49.5 


18,673 


602 


2,025 


2.7 


91 


48 


84 


53 


68. 5 


94 


13 


91 


25 


57. 8 


14, 372 


464 


1,582 


2. 1 


86 


40 


81 


46 


63. 2 


96 


14 


90 


23 


56. 4 


12,676 


423 


1,483 


2. 1 


83 


25 


70 


35 


52.8 


100 


18 


91 


31 


61.0 


9,862 


318 


1,381 


1.9 


65 


14 


54 


23 


38.4 


100 


18 


100 


34 


66.8 


6,602 


220 


1,300 


1. 8 


53 


— 5 


42 


9 


25.2 


100 


17 


99 


37 


67.5 


6,527 


211 


1, 155 


1.6 


97 


— 28 


65 


31 


47.5 


100 


8 


90 


28 


59.2 


146, 564 


401 


19,608 


2.2 



January. . 
February. 
March. . . . 

April 

May 

June 

July 

August . . . 
September 
October. . 
November 
December. 

Year. 





Precipi- 










Soil temperature, degrees Fah 


renheit 




































tation 




2-inch depth 




6-i 


nch depth 






12-inch depth 




Month 


in 
inches 


















































water 


Extreme 


Mean 




Extreme 


Mean 




Extreme 


Mean 














Mean 






Mean 








Mean 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 




January 


1.80 


30 


20 


27 


23 


24. 9 


30 


21 


27 


24 


25.3 


30 


21 


28 


23 


25. 6 


February 


1.25 


35 


24 


32 


27 


29.5 


35 


24 


32 


27 


29.4 


34 


22 


31 


27 


28.9 


March 


.90 


64 


24 


44 


29 


36. 1 


56 


25 


38 


30 


34.0 


46 


25 


35 


30 


32. 1 


April 


.55 


73 


29 


60 


37 


48.5 


62 


32 


54 


40 


47.2 


52 


34 


47 


42 


44.6 


May 


. 10 


100 


42 


86 


53 


69.6 


81 


47 


73 


58 


65.6 


70 


48 


63 


47 


60. 1 


June 


.06 


116 


53 


102 


66 


83.6 


93 


58 


83 


68 


75.3 


80 


61 


72 


67 


69.6 


July 


1.98 

4. 15 


118 
105 


62 
62 


103 
93 


73 
68 


87.8 
80. 5 


98 
95 


63 
62 


91 
84 


74 
68 


82.6 
76.0 


87 
87 


68 
65 


81 

77 


75 

71 


78.2 


August 


74. 


September 


.51 


94 


50 


87 


59 


72. 7 


82 


49 


74 


58 


66. 1 


73 


55 


67 


62 


64.3 


October 


1.65 


84 


36 


69 


46 


57.5 


68 


34 


57 


45 


50.8 


62 


40 


54 


49 


51.4 




.97 


56 


24 


43 


31 


37. 1 


45 


22 


35 


28 


31.6 


42 


24 


36 


31 


33.4 


December 


.60 


32 


13 


27 


19 


22.6 


28 


12 


21 


15 


18.3 


29 


18 


24 


20 


21.6 


Year 


14.52 


118 


13 


64 


44 


54.2 


98 


12 


56 


45 


50.2 


87 


18 


51 


45 


48.6 



Note.— Italic figures represent a sample size of less than 28 days. 



70 



APPENDIX— ANNUAL SUMMARIES— Continued 

Station: C-3; elevation: 6,500 feet; site: Canyon slope, northeast-facing; year: 1962 





Air temperature, 


degrees F. 


Percent relative humidity 


Solar radiation, 


Wind 


Month 


Extreme 


M< 


an 


Mean 


Extreme 


Mean 


Mean 


G-cal./sq. cm. 


Total 

miles 


Veloc- 
ity 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Total 


Mean 


m.p.h. 




48 
57 
66 
80 
83 
94 
95 
100 
93 
78 
68 
54 


-2 

-1 

5 

27 

26 

43 

54 

48 

41 

36 

18 

4 


38 
43 
45 
66 
71 
82 
90 
90 
79 
67 
54 
43 


16 
24 
23 
37 
40 
48 
57 
56 
51 
41 
32 
23 


26.9 
33.7 
34.0 
51.2 
55.5 
65. 1 
73. 7 
73. 1 
65.3 
54.0 
43.3 
33.0 


100 
100 
100 
100 
100 
92 
100 
100 
100 
100 
100 
100 


34 
28 
21 
17 
10 
14 
11 
10 
17 
12 
25 
29 


95 
96 
84 
73 
63 
53 
65 
55 
71 
85 
85 
95 


46 
48 
37 
28 

25 
21 
20 
21 
34 
37 
46 
49 


70.8 
72.2 
60. 3 
50. 7 
44. 1 
36. 9 
42. 6 
38.2 
52.2 
60. 7 
65.8 
72.0 










February 




























May 




















July 




































































Year 


100 


-2 


64 


37 


50.7 


100 


10 


77 


34 


55.5 























Precipi- 
tation 

in 
inches 
water 


Soil temperature, degrees Fahrenheit 


Month 


2-inch depth 


6-inch depth 


12-inch depth 




Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 




January 


































February 


































March 


































April 




































































June 


































July 


































August 


































September 


































October 


































November 




47 
35 


22 
14 


37 
26 


26 
21 


31. 5 
23.9 


41 
35 


27 
24 


36 
29 


31 

26 


J3. 7 
27.8 


40 
32 


27 
19 


35 
27 


32 

24 


33. 4 


December 




25. 7 








Year 





































































Note.— Italic figures represent a sample size of less than 28 days. 



71 



APPENDIX —ANNUAL SUMMARIES— Continued 

Station: C-3; elevation: 6,5C0 feet; site: Canyon slope, northeiist-facing; year: 1963 





Air temperature, degrees 


F. 


Percent relative humidity 


Solar radiation, 


Wind 


Month 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


G-cal./Sq. cm. 


Total 

miles 


Veloc- 
ity 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Total 


Mean 


m.p.h. 




44 
62 
68 
78 
86 
97 
102 
94 
88 
86 
65 
52 


-19 
4 
13 
18 
34 
38 
54 
52 
47 
32 
18 
5 


35 

46 
50 
60 
78 
85 
92 
83 
81 
71 
52 
40 


12 
25 
26 
31 
45 
49 
59 
56 
52 
43 
29 
18 


23. 7 
35. 1 
38.0 
45.6 
61.7 
66.7 
75.4 
69.3 
66.4 
57. 1 
40.8 
28.7 


100 

100 

100 

100 

99 

90 

99 

99 

100 

100 

100 

100 


26 
22 
16 
13 
12 
10 
14 
16 
14 
16 
26 
21 


93 
93 
86 
68 
52 
51 
61 
87 
73 
66 
85 
83 


56 
44 
34 
26 
18 
20 
22 
30 
27 
32 
38 
41 


74.6 
68.5 
60. 1 
46.7 
35.2 
35.5 
41.2 
58.3 
50.0 
48. 7 
61.3 
62.0 










March 


















April 

May 




























lulv 




















September 
















































Year 


102 


-19 


64 


37 


50. 7 


100 


10 


75 


32 


53.5 























Precipi- 
tation 

in 
inches 

water 










Soil temperature, degrees Fahrenheit 










Month 




2-i 


nch depth 




6-inch depth 




12- 


inch depth 






Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 


Extreme 


Mean 


Mean 




Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 


Max. 


Min. 




January 




32 

39 

69 

78 

100 

120 

120 

117 

98 

90 

56 

29 


19 
25 
26 
32 
48 
54 
62 
60 
52 
35 
24 
14 


29 
34 
47 
67 
90 
106 
109 
97 
90 
73 
42 
25 


25 
30 
32 
42 
58 
65 
72 
67 
59 
46 
29 
19 


26.7 
31.8 
39.4 
54.5 
74. 1 
85. 1 
90.4 
82.0 
74.4 
59.4 
35.6 
21. 7 


32 
35 
57 
65 
83 
94 
98 
97 
83 
73 
48 
30 


23 
27 
29 
37 
52 
63 
68 
65 
58 
42 
27 
20 


29 
33 
41 
58 
76 
86 
93 
86 
77 
61 
39 
25 


26 
30 
34 
46 
62 
71 
77 
72 
64 
51 
33 
22 


27.7 
31.5 
37.5 
52. 1 
69.3 
78.3 
85.0 
78.8 
70.5 
5(3. 3 
36.3 
23.8 


32 
36 
52 
60 
76 
83 
87 
87 
74 
65 
41 
30 


19 
25 
29 
40 
54 
63 
69 
65 
58 
41 
24 
18 


29 
33 
39 
54 
70 
76 
83 
78 
69 
55 
35 
22 


25 
29 
35 
49 
64 
69 
77 
72 
63 
51 
31 
20 


26.8 


February 




31.2 


March 




36. 9 


April 




51.3 


May 




66. 8 


June 




72.3 


July 




79. 8 


August 




74.7 


September 




66. 1 


October 




52.8 


November 




33.0 






20.8 








Year 




120 


14 


67 


45 


56.3 


98 


20 


59 


49 


53.9 


87 


18 


54 


49 


51.0 









Note.— Italic figures represent a sample size of less than 28 days. 



72 



US GOVERNMENT PRINTING OFFICE 1969 — 27I-47S 



r 



„ 



•^ 






o TTO<3TTT ~ 












y 






C 

i 

i 



<: 

CD 



C 
h